I pair of cranial nerves - the Olfactory nerves (n. olfactorius)The olfactory nerves or nerves of smell are distributed to the mucous membrane of the olfactory region of the nasal

cavity: this region comprises the superior nasal concha, and the corresponding part of the nasal septum. The nerves origi-nate from the central or deep processes of the olfactory cells of the nasal mucous membrane. They form a plexiform net-work in the mucous membrane, and are then collected into about twenty branches, which pierce the cribriform plate of the ethmoid bone in two groups, a lateral and a medial group, and end in the glomeruli of the olfactory bulb. Each branch re-ceives tubular sheaths from the dura mater and pia mater, the former being lost in the periosteum of the nose, the latter in the neurolemma of the nerve.

The olfactory nerves are non-medullated, and consist of axis-cylinders surrounded by nucleated sheaths, in which, however, there are fewer nuclei than are found in the sheaths of ordinary non-medullated nerve fibers.

The olfactory center in the cortex is generally associated with the rhinencephalon.The olfactary nerves are developed from the cells of the ectoderm which lines the olfactory pits; these cells undergo

proliferation and give rise to what are termed the olfactory cells of the nose. The axons of the olfactory cells grow into the overlying olfactory bulb and form the olfactory nerves.

II pair of cranial nerves - the Optic nerve (n. opticus)The optic nerve, or nerve of sight, consists mainly of fibers derived from the ganglionic cells of the retina. These

axons terminate in arborizations around the cells in the lateral geniculate body, pulvinar, and superior colliculus which con-stitute the lower or primary visual centers. From the cells of the lateral geniculate body and the pulvinar fibers pass to the cortical visual center, situated in the cuneus and in the neighborhood of the calcarine fissure. A few fibers of the optic nerve, of small caliber, pass from the primary centers to the retina and are supposed to govern chemical changes in the retina and also the movements of some of its elements (pigment cells and cones). There are also a few fine fibers, afferent fibers, extending from the retina to the brain, that are supposed to be concerned in pupillary reflexes.

The optic nerve is peculiar in that its fibers and ganglion cells are probably third in the series of neurons from the re-ceptors to the brain. Consequently the optic nerve corresponds rather to a tract of fibers within the brain than to the other cranial nerves. Its fibers pass backward and medialward through the orbit and optic foramen to the optic commissure where they partially decussate. The mixed fibers from the two nerves are continued in the optic tracts, the primary visual centers of the brain.

The orbital portion of the optic nerve is from 20 mm. to 30 mm. in length and has a slightly sinuous course to allow for movements of the eyeball. It is invested by an outer sheath of dura mater and an inner sheath from the arachnoid which are attached to the sclera around the area where the nerve fibers pierce the choroid and sclera of the bulb. A little behind the bulb of the eye the central artery of the retina with its accompanying vein perforates the optic nerve, and runs within it to the retina. As the nerve enters the optic foramen its dural sheath becomes continuous with that lining the orbit and the optic foramen. In the optic foramen the ophthalmic artery lies below and to its outer side. The intercranial portion of the optic nerve is about 10 mm. in length.

The Optic Chiasma (chiasma opticum), somewhat quadrilateral in form, rests upon the tuberculum sellae and on the anterior part of the diaphragma sellae. It is in relation, above, with the lamina terminalis; behind, with the tuber cinereum; on either side, with the anterior perforated substance. Within the chiasma, the optic nerves undergo a partial decussation. The fibers forming the medial part of each tract and posterior part of the chiasma have no connection with the optic nerves. They simply cross in the chiasma, and connect the medial geniculate bodies of the two sides; they form the commissure of Gudden. The remaining and principal part of the chiasma consists of two sets of fibers, crossed and uncrossed. The crossed fibers which are the more numerous, occupy the central part of the chiasma, and pass from the optic nerve of one side to the optic tract of the other, decussating in the chiasma with similar fibers of the opposite optic nerve. The uncrossed fibers occupy the lateral part of the chiasma, and pass from the nerve of one side into the tract of the same side.

The crossed fibers of the optic nerve tend to occupy the medial side of the nerve and the uncrossed fibers the lateral side. In the optic tract, however, the fibers are much more intermingled.

The Optic Tract passes backward and outward from the optic chiasma over the tuber cinereum and anterior perfo-rated space to the cerebral peduncle and winds obliquely across its under surface. Its fibers terminate in the lateral genicu-late body, the pulvinar and the superior colliculus. It is adherent to the tuber cinereum and the cerebral peduncle as it passes over them. In the region of the lateral geniculate body it splits into two bands. The medial and smaller one is a part of the commissure of Gudden and ends in the medial geniculate body.

From its mode of development, and from its structure, the optic nerve must be regarded as a prolongation of the brain substance, rather than as an ordinary cerebrospinal nerve. As it passes from the brain it receives sheaths from the three cerebral membranes, a perineural sheath from the pia mater, an intermediate sheath from the arachnoid, and an outer sheath from the dura mater, which is also connected with the periosteum as it passes through the optic foramen. These sheaths are separated from each other by cavities which communicate with the subdural and subarachnoid cavities respec -tively. The innermost or perineural sheath sends a process around the arteria centralis retinae into the interior of the nerve, and enters intimately into its structure.

III pair of cranial nerves - the Oculomotor nerve (n. oculomotorius)The oculomotor nerve supplies somatic motor fibers to all the ocular muscles, except the Obliquus superior and

Rectus lateralis; it also supplies through its connections with the ciliary ganglion, sympathetic motor fibers to the Sphincter pupillae and the Ciliaris muscles.

The fibers of the oculomotor nerve arise from a nucleus which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle. From this nucleus the fibers pass forward through the tegmentum, the red nucleus, and the medial part of the substantia nigra, forming a series of

curves with a lateral convexity, and emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.The nucleus of the oculomotor nerve does not consist of a continuous column of cells, but is broken up into a num-

ber of smaller nuclei, which are arranged in two groups, anterior and posterior. Those of the posterior group are six in num-ber, five of which are symmetrical on the two sides of the middle line, while the sixth is centrally placed and is common to the nerves of both sides. The anterior group consists of two nuclei, an antero-medial and an antero-lateral.

The nucleus of the oculomotor nerve, considered from a physiological standpoint, can be subdivided into several smaller groups of cells, each group controlling a particular muscle.

On emerging from the brain, the nerve is invested with a sheath of pia mater, and enclosed in a prolongation from the arachnoid. It passes between the superior cerebellar and posterior cerebral arteries, and then pierces the dura mater in front of and lateral to the posterior clinoid process, passing between the free and attached borders of the tentorium cerebelli. It runs along the lateral wall of the cavernous sinus, above the other orbital nerves, receiving in its course one or two fila -ments from the cavernous plexus of the sympathetic, and a communicating branch from the ophthalmic division of the trigeminal. It then divides into two branches, which enter the orbit through the superior orbital fissure, between the two heads of the Rectus lateralis. Here the nerve is placed below the trochlear nerve and the frontal and lacrimal branches of the ophthalmic nerve, while the nasociliary nerve is placed between its two rami.

The superior ramus, the smaller, passes medialward over the optic nerve, and supplies the Rectus superior and Lev-ator palpebrae superioris. The inferior ramus, the larger, divides into three branches. One passes beneath the optic nerve to the Rectus medialis; another, to the Rectus inferior; the third and longest runs forward between the Recti inferior and later -alis to the Obliquus inferior. From the last a short thick branch is given off to the lower part of the ciliary ganglion, and forms its short root. All these branches enter the muscles on their ocular surfaces, with the exception of the nerve to the Obliquus inferior, which enters the muscle at its posterior border.

IV pair of cranial nerves - the Trochlear nerve (n. trochlearis)The trochlear nerve, the smallest of the cranial nerves, supplies the Obliquus superior oculi.It arises from a nucleus situated in the floor of the cerebral aqueduct, opposite the upper part of the inferior collicu-

lus. From its origin it runs downward through the tegmentum, and then turns backward into the upper part of the anterior medullary velum. Here it decussates with its fellow of the opposite side and emerges from the surface of the velum at the side of the frenulum veli, immediately behind the inferior colliculus.

The nerve is directed across the superior cerebellar peduncle, and then winds forward around the cerebral peduncle, immediately above the pons, pierces the dura mater in the free border of the tentorium cerebelli, just behind, and lateral to, the posterior clinoid process, and passes forward in the lateral wall of the cavernous sinus, between the oculomotor nerve and the ophthalmic division of the trigeminal. It crosses the oculomotor nerve, and enters the orbit through the superior or -bital fissure. It now becomes the highest of all the nerves, and lies medial to the frontal nerve. In the orbit it passes medial -ward, above the origin of the Levator palpebrae superioris, and finally enters the orbital surface of the Obliquus superior.

In the lateral wall of the cavernous sinus the trochlear nerve forms communications with the ophthalmic division of the trigeminal and with the cavernous plexus of the sympathetic. In the superior orbital fissure it occasionally gives off a branch to the lacrimal nerve. It gives off a recurrent branch which passes backward between the layers of the tentorium cerebelli and divides into two or three filaments which may be traced as far as the wall of the transverse sinus.

VI pair of cranial nerves - the Abducent nerve (n. abducens)The abducent nerve supplies the Rectus lateralis oculi.Its fibers arise from a small nucleus situated in the upper part of the rhomboid fossa, close to the middle line and be -

neath the colliculus facialis. They pass downward and forward through the pons, and emerge in the furrow between the lower border of the pons and the upper end of the pyramid of the medulla oblongata.

From the nucleus of the sixth nerve, fibers are said to pass through the medial longitudinal fasciculus to the oculo -motor nerve of the opposite side, along which they are carried to the Rectus medialis. The Rectus lateralis of one eye and the Rectus medialis of the other may therefore be said to receive their nerves from the same nucleus.

The nerve pierces the dura mater on the dorsum sellae of the sphenoid, runs through a notch in the bone below the posterior clinoid process, and passes forward through the cavernous sinus, on the lateral side of the internal carotid artery. It enters the orbit through the superior orbital fissure, above the ophthalmic vein, from which it is separated by a lamina of dura mater. It then passes between the two heads of the Rectus lateralis, and enters the ocular surface of that muscle. The abducent nerve is joined by several filaments from the carotid and cavernous plexuses, and by one from the ophthalmic nerve. The oculomotor, trochlear, ophthalmic, and abducent nerves bear certain relations to each other in the cavernous si -nus, at the superior orbital fissure, and in the cavity of the orbit, as follows:

In the cavernous sinus the oculomotor, trochlear, and ophthalmic nerves are placed in the lateral wall of the sinus, in the order given, from above downward. The abducent nerve lies at the lateral side of the internal carotid artery. As these nerves pass forward to the superior orbital fissure, the oculomotor and ophthalmic divide into branches and the abducent nerve approaches the others; so that their relative positions are considerably changed.

In the superior orbital fissure the trochlear nerve and the frontal and lacrimal divisions of the ophthalmic lie in this order from the medial to the lateral side upon the same plane; they enter the cavity of the orbit above the muscles. The re -maining nerves enter the orbit between the two heads of the Rectus lateralis. The superior division of the oculomotor is the highest of these; beneath this lies the nasociliary branch of the ophthalmic; then the inferior division of the oculomotor; and the abducent lowest of all.

In the orbit, the trochlear, frontal, and lacrimal nerves lie immediately beneath the periosteum, the trochlear nerve resting on the Obliquus superior, the frontal on the Levator palpebrae superioris, and the lacrimal on the Rectus lateralis. The superior division of the oculomotor nerve lies immediately beneath the Rectus superior, while the nasociliary nerve crosses the optic nerve to reach the medial wall of the orbit. Beneath these is the optic nerve, surrounded in front by the cil-

iary nerves, and having the ciliary ganglion on its lateral side, between it and the Rectus lateralis. Below the optic nerve are the inferior division of the oculomotor, and the abducent, the latter lying on the medial surface of the Rectus lateralis.

XI pair of cranial nerves - the Accessory nerve (n. accessorius; spinal accessory nerve)The accessory nerve consists of two parts: a cranial and a spinal.The Cranial Part (ramus internus; accessory portion) is the smaller of the two. Its fibers arise from the cells of the

nucleus ambiguus and emerge as four or five delicate rootlets from the side of the medulla oblongata, below the roots of the vagus. It runs lateralward to the jugular foramen, where it interchanges fibers with the spinal portion or becomes united to it for a short distance; here it is also connected by one or two filaments with the jugular ganglion of the vagus. It then passes through the jugular foramen, separates from the spinal portion and is continued over the surface of the ganglion no-dosum of the vagus, to the surface of which it is adherent, and is distributed principally to the pharyngeal and superior la -ryngeal branches of the vagus. Through the pharyngeal branch it probably supplies the Musculus uvulae and Levator veli palatini. Some few filaments from it are continued into the trunk of the vagus below the ganglion, to be distributed with the recurrent nerve and probably also with the cardiac nerves.

The Spinal Part (ramus externus; spinal portion) is firm in texture, and its fibers arise from the motor cells in the lateral part of the anterior column of the gray substance of the medulla spinalis as low as the fifth cervical nerve. Passing through the lateral funiculus of the medulla spinalis, they emerge on its surface and unite to form a single trunk, which as-cends between the ligamentum denticulatum and the posterior roots of the spinal nerves; enters the skull through the fora -men magnum, and is then directed to the jugular foramen, through which it passes, lying in the same sheath of dura mater as the vagus, but separated from it by a fold of the arachnoid. In the jugular foramen, it receives one or two filaments from the cranial part of the nerve, or else joins it for a short distance and then separates from it again. As its exit from the jugular foramen, it runs backward in front of the internal jugular vein in 66.6 per cent. of cases, and behind in it 33.3 per cent. The nerve then descends obliquely behind the Digastricus and Stylohyoideus to the upper part of the Sternocleidomastoideus; it pierces this muscle, and courses obliquely across the posterior triangle of the neck, to end in the deep surface of the Trapez -ius. As it traverses the Sternocleidomastoideus it gives several filaments to the muscle, and joins with branches from the second cervical nerve. In the posterior triangle it unites with the second and third cervical nerves, while beneath the Trapez-ius it forms a plexus with the third and fourth cervical nerves, and from this plexus fibers are distributed to the muscle.

XII pair of cranial nerves - the Hypoglossal nerve (n. hypoglossus)The hypoglossal nerve is the motor nerve of the tongue.Its fibers arise from the cells of the hypoglossal nucleus, which is an upward prolongation of the base of the ante-

rior column of gray substance of the medulla spinalis. This nucleus is about 2 cm. in length, and its upper part corresponds with the trigonum hypoglossi, or lower portion of the medial eminence of the rhomboid fossa. The lower part of the nu -cleus extends downward into the closed part of the medulla oblongata, and there lies in relation to the ventro-lateral aspect of the central canal. The fibers run forward through the medulla oblongata, and emerge in the antero-lateral sulcus between the pyramid and the olive.

The rootlets of this nerve are collected into two bundles, which perforate the dura mater separately, opposite the hy -poglossal canal in the occipital bone, and unite together after their passage through it; in some cases the canal is divided into two by a small bony spicule. The nerve descends almost vertically to a point corresponding with the angle of the mandible. It is at first deeply seated beneath the internal carotid artery and internal jugular vein, and intimately connected with the vagus nerve; it then passes forward between the vein and artery, and lower down in the neck becomes superficial below the Digastricus. The nerve then loops around the occipital artery, and crosses the external carotid and lingual arteries below the tendon of the Digastricus. It passes beneath the tendon of the Digastricus, the Stylohyoideus, and the Mylohy -oideus, lying between the last-named muscle and the Hyoglossus, and communicates at the anterior border of the Hyoglos-sus with the lingual nerve; it is then continued forward in the fibers of the Genioglossus as far as the tip of the tongue, dis -tributing branches to its muscular substance.

Branches of Communication.—Its branches of communication are, with the Vagus, First and second cervical nerves, Sympathetic, Lingual.

The communications with the vagus take place close to the skull, numerous filaments passing between the hypoglos-sal and the ganglion nodosum of the vagus through the mass of connective tissue which unites the two nerves. As the nerve winds around the occipital artery it gives off a filament to the pharyngeal plexus.

The communication with the sympathetic takes place opposite the atlas by branches derived from the superior cervi -cal ganglion, and in the same situation the nerve is joined by a filament derived from the loop connecting the first and sec -ond cervical nerves.

The communications with the lingual take place near the anterior border of the Hyoglossus by numerous filaments which ascend upon the muscle.

Branches of Distribution.—The branches of distribution of the hypoglossal nerve are: Meningeal, Thyrohyoid, De-scending, Muscular.

Of these branches, the meningeal, descending, thyrohyoid, and the muscular twig to the Geniohyoideus, are probably derived mainly from the branch which passes from the loop between the first and second cervical to join the hypoglossal.

Meningeal Branches (dural branches).—As the hypoglossal nerve passes through the hypoglossal canal it gives off, according to Luschka, several filaments to the dura mater in the posterior fossa of the skull.

The Descending Ramus (ramus descendens; descendens hypoglossi), long and slender, quits the hypoglossal where it turns around the occipital artery and descends in front of or in the sheath of the carotid vessels; it gives a branch to the su-perior belly of the Omohyoideus, and then joins the communicantes cervicales from the second and third cervical nerves; just below the middle of the neck, to form a loop, the ansa hypoglossi. From the convexity of this loop branches pass to supply the Sternohyoideus, the Sternothyreoideus, and the inferior belly of the Omohyoideus. According to Arnold, another

filament descends in front of the vessels into the thorax, and joins the cardiac and phrenic nerves.The Thyrohyoid Branch (ramus thyreohyoideus) arises from the hypoglossal near the posterior border of the hyo-

glossus; it runs obliquely across the greater cornu of the hyoid bone, and supplies the Thyreohyoideus muscle.The Muscular Branches are distributed to the Styloglossus, Hyoglossus, Geniohyoideus, and Genioglossus. At the

under surface of the tongue numerous slender branches pass upward into the substance of the organ to supply its intrinsic muscles.

Practice skillsStudents are supposed to identify the following structures on the samples:

- optic nerve (II pair)- oculomotor nerve (III pair) - trochlear nerve (IV pair)

- abducent nerve (VI pair) - accessory nerve (XI pair) - hypoglossal nerve (ХП pair)

Practice class 9. V pair of cranial nerves: the trigeminal nerve. The innervation of skin of the head.

The aim: to learn the trigeminal nerve, its branches and objects of innervation; to understand the innerva-tion of the skin of the head.

Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-sents special interest for therapists, neurologists, neuropathologists and others.

The plan of the practice class:A. Checking of the home assignment: oral quiz or written test control – 30 minutes.B. Summary lecture on the topic by teacher – 30 minutes.

a) The general characteristic of nuclei, roots and ganglion of the trigeminal nerve.b) The ophthalmic nerve and its branches.c) The maxillary nerve and its branches.d) The mandibular nerve and its branches.

C. Students’ self-taught time – 55 minutesD. Home-task – 5 minutes

The Trigeminal Nerve (N. Trigeminus; Fifth Or Trifacial Nerve)The trigeminal nerve is the largest cranial nerve and is the great sensory nerve of the head and face, and the motor

nerve of the muscles of mastication.It emerges from the side of the pons, near its upper border, by a small motor and a large sensory root—the former

being situated in front of and medial to the latter.Motor Root.—The fibers of the motor root arise from two nuclei, a superior and an inferior. The superior nucleus

consists of a strand of cells occupying the whole length of the lateral portion of the gray substance of the cerebral aqueduct. The inferior or chief nucleus is situated in the upper part of the pons, close to its dorsal surface, and along the line of the lateral margin of the rhomboid fossa. The fibers from the superior nucleus constitute the mesencephalic root: they descend through the mid-brain, and, entering the pons, join with the fibers from the lower nucleus, and the motor root, thus formed, passes forward through the pons to its point of emergence. It is uncertain whether the mesencephalic root is motor or sen -sory.

Sensory Root.—The fibers of the sensory root arise from the cells of the semilunar ganglion which lies in a cavity of the dura mater near the apex of the petrous part of the temporal bone. They pass backward below the superior petrosal si-nus and tentorium cerebelli, and, entering the pons, divide into upper and lower roots. The upper root ends partly in a nu -cleus which is situated in the pons lateral to the lower motor nucleus, and partly in the locus caeruleus; the lower root de -scends through the pons and medulla oblongata, and ends in the upper part of the substantia gelatinosa of Rolando. This lower root is sometimes named the spinal root of the nerve. Medullation of the fibers of the sensory root begins about the fifth month of fetal life, but the whole of its fibers are not medullated until the third month after birth.

The Semilunar Ganglion (ganglion semilunare [Gasseri]; Gasserian ganglion) occupies a cavity (cavum Meckelii) in the dura mater covering the trigeminal impression near the apex of the petrous part of the temporal bone. It is somewhat crescentic in shape, with its convexity directed forward: medially, it is in relation with the internal carotid artery and the posterior part of the cavernous sinus. The motor root runs in front of and medial to the sensory root, and passes beneath the ganglion; it leaves the skull through the foramen ovale, and, immediately below this foramen, joins the mandibular nerve. The greater superficial petrosal nerve lies also underneath the ganglion.

The ganglion receives, on its medial side, filaments from the carotid plexus of the sympathetic. It gives off minute branches to the tentorium cerebelli, and to the dura mater in the middle fossa of the cranium. From its convex border, which is directed forward and lateralward, three large nerves proceed, viz., the ophthalmic, maxillary, and mandibular. The ophthalmic and maxillary consist exclusively of sensory fibers; the mandibular is joined outside the cranium by the motor root.

Associated with the three divisions of the trigeminal nerve are four small ganglia. The ciliary ganglion is connected with the ophthalmic nerve; the sphenopalatine ganglion with the maxillary nerve; and the otic and submaxillary ganglia

with the mandibular nerve. All four receive sensory filaments from the trigeminal, and motor and sympathetic filaments from various sources; these filaments are called the roots of the ganglia.

The Ophthalmic Nerve (n. ophthalmicus), or first division of the trigeminal, is a sensory nerve. It supplies branches to the cornea, ciliary body, and iris; to the lacrimal gland and conjunctiva; to the part of the mucous membrane of the nasal cavity; and to the skin of the eyelids, eyebrow, forehead, and nose. It is the smallest of the three divisions of the trigeminal, and arises from the upper part of the semilunar ganglion as a short, flattened band, about 2.5 cm. long, which passes forward along the lateral wall of the cavernous sinus, below the oculomotor and trochlear nerves; just before enter-ing the orbit, through the superior orbital fissure, it divides into three branches, lacrimal, frontal, and nasociliary.

The ophthalmic nerve is joined by filaments from the cavernous plexus of the sympathetic, and communicates with the oculomotor, trochlear, and abducent nerves; it gives off a recurrent filament which passes between the layers of the ten -torium.

The Lacrimal Nerve (n. lacrimalis) is the smallest of the three branches of the ophthalmic. It sometimes receives a filament from the trochlear nerve, but this is possibly derived from the branch which goes from the ophthalmic to the trochlear nerve. It passes forward in a separate tube of dura mater, and enters the orbit through the narrowest part of the su-perior orbital fissure. In the orbit it runs along the upper border of the Rectus lateralis, with the lacrimal artery, and commu-nicates with the zygomatic branch of the maxillary nerve. It enters the lacrimal gland and gives off several filaments, which supply the gland and the conjunctiva. Finally it pierces the orbital septum, and ends in the skin of the upper eyelid, joining with filaments of the facial nerve. The lacrimal nerve is occasionally absent, and its place is then taken by the zygomati-cotemporal branch of the maxillary. Sometimes the latter branch is absent, and a continuation of the lacrimal is substituted for it.

The Frontal Nerve (n. frontalis) is the largest branch of the ophthalmic, and may be regarded, both from its size and direction, as the continuation of the nerve. It enters the orbit through the superior orbital fissure, and runs forward between the Levator palpebrae superioris and the periosteum. Midway between the apex and base of the orbit it divides into two branches, supratrochlear and supraorbital.

The supratrochlear nerve (n. supratrochlearis), the smaller of the two, passes above the pulley of the Obliquus su-perior, and gives off a descending filament, to join the infratrochlear branch of the nasociliary nerve. It then escapes from the orbit between the pulley of the Obliquus superior and the supraorbital foramen, curves up on to the forehead close to the bone, ascends beneath the Corrugator and Frontalis, and dividing into branches which pierce these muscles, it supplies the skin of the lower part of the forehead close to the middle line and sends filaments to the conjunctiva and skin of the upper eyelid.

The supraorbital nerve (n. supraorbitalis) passes through the supraorbital foramen, and gives off, in this situation, palpebral filaments to the upper eyelid. It then ascends upon the forehead, and ends in two branches, a medial and a lateral, which supply the integument of the scalp, reaching nearly as far back as the lambdoidal suture; they are at first situated be-neath the Frontalis, the medial branch perforating the muscle, the lateral branch the galea aponeurotica. Both branches sup-ply small twigs to the pericranium.

The Nasociliary Nerve (n. nasociliaris; nasal nerve) is intermediate in size between the frontal and lacrimal, and is more deeply placed. It enters the orbit between the two heads of the Rectus lateralis, and between the superior and inferior rami of the oculomotor nerve. It passes across the optic nerve and runs obliquely beneath the Rectus superior and Obliquus superior, to the medial wall of the orbital cavity. Here it passes through the anterior ethmoidal foramen, and, entering the cavity of the cranium, traverses a shallow groove on the lateral margin of the front part of the cribriform plate of the eth -moid bone, and runs down, through a slit at the side of the crista galli, into the nasal cavity. It supplies internal nasal branches to the mucous membrane of the front part of the septum and lateral wall of the nasal cavity. Finally, it emerges, as the external nasal branch, between the lower border of the nasal bone and the lateral nasal cartilage, and, passing down beneath the Nasalis muscle, supplies the skin of the ala and apex of the nose.

The nasociliary nerve gives off the following branches, viz.: the long root of the ciliary ganglion, the long ciliary, and the ethmoidal nerves.

The long root of the ciliary ganglion (radix longa ganglii ciliaris) usually arises from the nasociliary between the two heads of the Rectus lateralis. It passes forward on the lateral side of the optic nerve, and enters the postero-superior an -gle of the ciliary ganglion; it is sometimes joined by a filament from the cavernous plexus of the sympathetic, or from the superior ramus of the trochlear nerve.

The long ciliary nerves (nn. ciliares longi), two or three in number, are given off from the nasociliary, as it crosses the optic nerve. They accompany the short ciliary nerves from the ciliary ganglion, pierce the posterior part of the sclera, and running forward between it and the choroid, are distributed to the iris and cornea. The long ciliary nerves are supposed to contain sympathetic fibers from the superior cervical ganglion to the Dilator pupillae muscle.

The infratrochlear nerve (n. infratrochlearis) is given off from the nasociliary just before it enters the anterior eth-moidal foramen. It runs forward along the upper border of the Rectus medialis, and is joined, near the pulley of the Obliquus superior, by a filament from the supratrochlear nerve. It then passes to the medial angle of the eye, and supplies the skin of the eyelids and side of the nose, the conjunctiva, lacrimal sac, and caruncula lacrimalis.

The ethmoidal branches (nn. ethmoidales) supply the ethmoidal cells; the posterior branch leaves the orbital cavity through the posterior ethmoidal foramen and gives some filaments to the sphenoidal sinus.

The Ciliary Ganglion (ophthalmic or lenticular ganglion).—The ciliary ganglion is a small, sympathetic ganglion, of a reddish-gray color, and about the size of a pin’s head; it is situated at the back part of the orbit, in some loose fat be -tween the optic nerve and the Rectus lateralis muscle, lying generally on the lateral side of the ophthalmic artery.

Its roots are three in number, and enter its posterior border. One, the long or sensory root, is derived from the nasociliary nerve, and joins its postero-superior angle. The second, the short or motor root, is a thick nerve (occasionally di-

vided into two parts) derived from the branch of the oculomotor nerve to the Obliquus inferior, and connected with the pos-tero-inferior angle of the ganglion. The motor root is supposed to contain sympathetic efferent fibers (preganglionic fibers) from the nucleus of the third nerve in the mid-brain to the ciliary ganglion where they form synapses with neurons whose fibers (postganglionic) pass to the Ciliary muscle and to Sphincter muscle of the pupil. The third, the sympathetic root, is a slender filament from the cavernous plexus of the sympathetic; it is frequently blended with the long root. According to Tiedemann, the ciliary ganglion receives a twig of communication from the sphenopalatine ganglion.

Its branches are the short ciliary nerves. These are delicate filaments, from six to ten in number, which arise from the forepart of the ganglion in two bundles connected with its superior and inferior angles; the lower bundle is the larger. They run forward with the ciliary arteries in a wavy course, one set above and the other below the optic nerve, and are ac -companied by the long ciliary nerves from the nasociliary. They pierce the sclera at the back part of the bulb of the eye, pass forward in delicate grooves on the inner surface of the sclera, and are distributed to the Ciliaris muscle, iris, and cornea. Tiedemann has described a small branch as penetrating the optic nerve with the arteria centralis retinae.

The Maxillary Nerve (n. maxillaris; superior maxillary nerve), or second division of the trigeminal, is a sensory nerve. It is intermediate, both in position and size, between the ophthalmic and mandibular. It begins at the middle of the semilunar ganglion as a flattened plexiform band, and, passing horizontally forward, it leaves the skull through the foramen rotundum, where it becomes more cylindrical in form, and firmer in texture. It then crosses the pterygopalatine fossa, in -clines lateralward on the back of the maxilla, and enters the orbit through the inferior orbital fissure; it traverses the infraor -bital groove and canal in the floor of the orbit, and appears upon the face at the infraorbital foramen. At its termination, the nerve lies beneath the Quadratus labii superioris, and divides into a leash of branches which spread out upon the side of the nose, the lower eyelid, and the upper lip, joining with filaments of the facial nerve.

Branches.—Its branches may be divided into four groups, according as they are given off in the cranium, in the pterygopalatine fossa, in the infraorbital canal, or on the face.

In the Cranium – Middle meningeal.In the Pterygopalatine Fossa – Zygomatic, Sphenopalatine, Posterior superior alveolar.In the Infraorbital Canal – Anterior superior alveolar, Middle superior alveolar.On the Face – Inferior palpebral, External nasal, Superior labial.The Middle Meningeal Nerve (n. meningeus medius; meningeal or dural branch) is given off from the maxillary

nerve directly after its origin from the semilunar ganglion; it accompanies the middle meningeal artery and supplies the dura mater.

The Zygomatic Nerve (n. zygomaticus; temporomalar nerve; orbital nerve) arises in the pterygopalatine fossa, en-ters the orbit by the inferior orbital fissure, and divides at the back of that cavity into two branches, zygomaticotemporal and zygomaticofacial.

The zygomaticotemporal branch (ramus zygomaticotemporalis; temporal branch) runs along the lateral wall of the orbit in a groove in the zygomatic bone, receives a branch of communication from the lacrimal, and, passing through a foramen in the zygomatic bone, enters the temporal fossa. It ascends between the bone, and substance of the Temporalis muscle, pierces the temporal fascia about 2.5 cm. above the zygomatic arch, and is distributed to the skin of the side of the forehead, and communicates with the facial nerve and with the aurićulotemporal branch of the mandibular nerve. As it pierces the temporal fascia, it gives off a slender twig, which runs between the two layers of the fascia to the lateral angle of the orbit.

The zygomaticofacial branch (ramus zygomaticofacialis; malar branch) passes along the infero-lateral angle of the orbit, emerges upon the face through a foramen in the zygomatic bone, and, perforating the Orbicularis oculi, supplies the skin on the prominence of the cheek. It joins with the facial nerve and with the inferior palpebral branches of the maxillary.

The Sphenopalatine Branches (nn. sphenopalatini), two in number, descend to the sphenopalatine ganglion.The Posterior Superior Alveolar Branches (rami alveolares superiores posteriores; posterior superior dental

branches) arise from the trunk of the nerve just before it enters the infraorbital groove; they are generally two in number, but sometimes arise by a single trunk. They descend on the tuberosity of the maxilla and give off several twigs to the gums and neighboring parts of the mucous membrane of the cheek. They then enter the posterior alveolar canals on the infratem-poral surface of the maxilla, and, passing from behind forward in the substance of the bone, communicate with the middle superior alveolar nerve, and give off branches to the lining membrane of the maxillary sinus and three twigs to each molar tooth; these twigs enter the foramina at the apices of the roots of the teeth.

The Middle Superior Alveolar Branch (ramus alveolaris superior medius; middle superior dental branch), is given off from the nerve in the posterior part of the infraorbital canal, and runs downward and forward in a canal in the lat -eral wall of the maxillary sinus to supply the two premolar teeth. It forms a superior dental plexus with the anterior and posterior superior alveolar branches.

The Anterior Superior Alveolar Branch (ramus alveolaris superior anteriores; anterior superior dental branch), of considerable size, is given off from the nerve just before its exit from the infraorbital foramen; it descends in a canal in the anterior wall of the maxillary sinus, and divides into branches which supply the incisor and canine teeth. It communi-cates with the middle superior alveolar branch, and gives off a nasal branch, which passes through a minute canal in the lateral wall of the inferior meatus, and supplies the mucous membrane of the anterior part of the inferior meatus and the floor of the nasal cavity, communicating with the nasal branches from the sphenopalatine ganglion.

The Inferior Palpebral Branches (rami palpebrales inferiores; palpebral branches) ascend behind the Orbicularis oculi. They supply the skin and conjunctiva of the lower eyelid, joining at the lateral angle of the orbit with the facial and zygomaticofacial nerves.

The External Nasal Branches (rami nasales externi) supply the skin of the side of the nose and of the septum mo-bile nasi, and join with the terminal twigs of the nasociliary nerve.

The Superior Labial Branches (rami labiales superiores; labial branches), the largest and most numerous, de-scend behind the Quadratus labii superioris, and are distributed to the skin of the upper lip, the mucous membrane of the mouth, and labial glands. They are joined, immediately beneath the orbit, by filaments from the facial nerve, forming with them the infraorbital plexus.

Sphenopalatine Ganglion (ganglion of Meckel).—The sphenopalatine ganglion, the largest of the sympathetic ganglia associated with the branches of the trigeminal nerve, is deeply placed in the pterygopalatine fossa, close to the sphenopalatine foramen. It is triangular or heart-shaped, of a reddish-gray color, and is situated just below the maxillary nerve as it crosses the fossa. It receives a sensory, a motor, and a sympathetic root.

Its sensory root is derived from two sphenopalatine branches of the maxillary nerve; their fibers, for the most part, pass directly into the palatine nerves; a few, however, enter the ganglion, constituting its sensory root. Its motor root is probably derived from the nervus intermedius through the greater superficial petrosal nerve and is supposed to consist in part of sympathetic efferent (preganglionic) fibers from the medulla. In the sphenopalatine ganglion they form synapses with neurons whose postganglionic axons, vasodilator and secretory fibers, are distributed with the deep branches of the trigeminal to the mucous membrane of the nose, soft palate, tonsils, uvula, roof of the mouth, upper lip and gums, and to the upper part of the pharynx. Its sympathetic root is derived from the carotid plexus through the deep petrosal nerve. These two nerves join to form the nerve of the pterygoid canal before their entrance into the ganglion.

The greater superficial petrosal nerve (n. petrosus superficialis major; large superficial petrosal nerve) is given off from the genicular ganglion of the facial nerve; it passes through the hiatus of the facial canal, enters the cranial cavity, and runs forward beneath the dura mater in a groove on the anterior surface of the petrous portion of the temporal bone. It then enters the cartilaginous substance which fills the foramen lacerum, and joining with the deep petrosal branch forms the nerve of the pterygoid canal.

The deep petrosal nerve (n. petrosus profundus; large deep petrosal nerve) is given off from the carotid plexus, and runs through the carotid canal lateral to the internal carotid artery. It then enters the cartilaginous substance which fills the foramen lacerum, and joins with the greater superficial petrosal nerve to form the nerve of the pterygoid canal.

The nerve of the pterygoid canal (n. canalis pterygoidei [Vidii]; Vidian nerve), formed by the junction of the two preceding nerves in the cartilaginous substance which fills the foramen lacerum, passes forward, through the pterygoid canal, with the corresponding artery, and is joined by a small ascending sphenoidal branch from the otic ganglion. Finally, it enters the pterygopalatine fossa, and joins the posterior angle of the sphenopalatine ganglion.

Branches of Distribution.—These are divisible into four groups, viz., orbital, palatine, posterior superior nasal, and pharyngeal.

The orbital branches (rami orbitales; ascending branches) are two or three delicate filaments, which enter the orbit by the inferior orbital fissure, and supply the periosteum. According to Luschka, some filaments pass through foramina in the frontoethmoidal suture to supply the mucous membrane of the posterior ethmoidal and sphenoidal sinuses.

The palatine nerves (nn. palatini; descending branches) are distributed to the roof of the mouth, soft palate, tonsil, and lining membrane of the nasal cavity. Most of their fibers are derived from the sphenopalatine branches of the maxillary nerve. They are three in number: anterior, middle, and posterior.

The anterior palatine nerve (n. palatinus anterior) descends through the pterygopalatine canal, emerges upon the hard palate through the greater palatine foramen, and passes forward in a groove in the hard palate, nearly as far as the in-cisor teeth. It supplies the gums, the mucous membrane and glands of the hard palate, and communicates in front with the terminal filaments of the nasopalatine nerve. While in the pterygopalatine canal, it gives off posterior inferior nasal branches, which enter the nasal cavity through openings in the palatine bone, and ramify over the inferior nasal concha and middle and inferior meatuses; at its exit from the canal, a palatine branch is distributed to both surfaces of the soft palate.

The middle palatine nerve (n. palatinus medius) emerges through one of the minor palatine canals and distributes branches to the uvula, tonsil, and soft palate. It is occasionally wanting.

The posterior palatine nerve (n. palatinus posterior) descends through the pterygopalatine canal, and emerges by a separate opening behind the greater palatine foramen; it supplies the soft palate, tonsil, and uvula. The middle and posterior palatine join with the tonsillar branches of the glossopharyngeal to form a plexus (circulus tonsillaris) around the tonsil.

The posterior superior nasal branches (rami nasales posteriores superiores) are distributed to the septum and lat-eral wall of the nasal fossa. They enter the posterior part of the nasal cavity by the sphenopalatine foramen and supply the mucous membrane covering the superior and middle nasal conchae, the lining of the posterior ethmoidal cells, and the pos -terior part of the septum. One branch, longer and larger than the others, is named the nasopalatine nerve. It enters the nasal cavity through the sphenopalatine foramen, passes across the roof of the nasal cavity below the orifice of the sphe-noidal sinus to reach the septum, and then runs obliquely downward and forward between the periosteum and mucous membrane of the lower part of the septum. It descends to the roof of the mouth through the incisive canal and communi -cates with the corresponding nerve of the opposite side and with the anterior palatine nerve. It furnishes a few filaments to the mucous membrane of the nasal septum.The pharyngeal nerve (pterygopalatine nerve) is a small branch arising from the posterior part of the ganglion. It passes through the pharyngeal canal with the pharyngeal branch of the internal maxillary artery, and is distributed to the mucous membrane of the nasal part of the pharynx, behind the auditory tube.

The mandibular nerve (n. mandibularis; inferior maxillary nerve) supplies the teeth and gums of the mandible, the skin of the temporal region, the auricula, the lower lip, the lower part of the face, and the muscles of mastication; it also supplies the mucous membrane of the anterior two-thirds of the tongue. It is the largest of the three divisions of the fifth, and is made up of two roots: a large, sensory root proceeding from the inferior angle of the semilunar ganglion, and a small motor root (the motor part of the trigeminal), which passes beneath the ganglion, and unites with the sensory root, just after its exit through the foramen ovale. Immediately beneath the base of the skull, the nerve gives off from its medial

side a recurrent branch (nervus spinosus) and the nerve to the Pterygoideus internus, and then divides into two trunks, an anterior and a posterior.

The Nervus Spinosus (recurrent or meningeal branch) enters the skull through the foramen spinosum with the mid-dle meningeal artery. It divides into two branches, anterior and posterior, which accompany the main divisions of the artery and supply the dura mater; the posterior branch also supplies the mucous lining of the mastoid cells; the anterior communi -cates with the meningeal branch of the maxillary nerve.

The Internal Pterygoid Nerve (n. pterygoideus internus).—The nerve to the Pterygoideus internus is a slender branch, which enters the deep surface of the muscle; it gives off one or two filaments to the otic ganglion.

The anterior and smaller division of the mandibular nerve receives nearly the whole of the fibers of the motor root of the nerve, and supplies the muscles of mastication and the skin and mucous membrane of the cheek. Its branches are the masseteric, deep temporal, buccinator, and external pterygoid.

The Masseteric Nerve (n. massetericus) passes lateralward, above the Pterygoideus externus, in front of the tem-poromandibular articulation, and behind the tendon of the Temporalis; it crosses the mandibular notch with the masseteric artery, to the deep surface of the Masseter, in which it ramifies nearly as far as its anterior border. It gives a filament to the temporomandibular joint.

The Deep Temporal Nerves (nn. temporales profundi) are two in number, anterior and posterior. They pass above the upper border of the Pterygoideus externus and enter the deep surface of the Temporalis. The posterior branch, of small size, is placed at the back of the temporal fossa, and sometimes arises in common with the masseteric nerve. The anterior branch is frequently given off from the buccinator nerve, and then turns upward over the upper head of the Pterygoideus externus. Frequently a third or intermediate branch is present.

The Buccinator Nerve (n. buccinatorus; long buccal nerve) passes forward between the two heads of the Ptery-goideus externus, and downward beneath or through the lower part of the Temporalis; it emerges from under the anterior border of the Masseter, ramifies on the surface of the Buccinator, and unites with the buccal branches of the facial nerve. It supplies a branch to the Pterygoideus externus during its passage through that muscle, and may give off the anterior deep temporal nerve. The buccinator nerve supplies the skin over the Buccinator, and the mucous membrane lining its inner sur-face.

External Pterygoid Nerve (n. pterygoideus externus).—The nerve to the Pterygoideus externus frequently arises in conjunction with the buccinator nerve, but it may be given off separately from the anterior division of the mandibular nerve. It enters the deep surface of the muscle.

The posterior and larger division of the mandibular nerve is for the most part sensory, but receives a few filaments from the motor root. It divides into auriculotemporal, lingual, and inferior alveolar nerves.

The Auriculotemporal Nerve (n. auriculotemporalis) generally arises by two roots, between which the middle meningeal artery ascends. It runs backward beneath the Pterygoideus externus to the medial side of the neck of the mandible. It then turns upward with the superficial temporal artery, between the auricula and condyle of the mandible, un -der cover of the parotid gland; escaping from beneath the gland, it ascends over the zygomatic arch, and divides into super -ficial temporal branches.

The branches of communication of the auriculotemporal nerve are with the facial nerve and with the otic ganglion. The branches to the facial, usually two in number, pass forward from behind the neck of the mandible and join the facial nerve at the posterior border of the Masseter. The filaments to the otic ganglion are derived from the roots of the auricu -lotemporal nerve close to their origin.

Its branches of distribution are:Anterior auricular, Articular, Branches to the external acoustic meatus, Parotid, Superficial temporal.The anterior auricular branches (nn. auriculares anteriores) are usually two in number; they supply the front of

the upper part of the auricula, being distributed principally to the skin covering the front of the helix and tragus.The branches to the external acoustic meatus (n. meatus auditorii externi), two in number, enter the meatus be-

tween its bony and cartilaginous portions and supply the skin lining it; the upper one sends a filament to the tympanic membrane.

The articular branches consist of one or two twigs which enter the posterior part of the temporomandibular joint.The parotid branches (rami parotidei) supply the parotid gland.The superficial temporal branches (rami temporales superficiales) accompany the superficial temporal artery to

the vertex of the skull; they supply the skin of the temporal region and communicate with the facial and zygomaticotempo-ral nerves.

The Lingual Nerve (n. lingualis) supplies the mucous membrane of the anterior two-thirds of the tongue. It lies at first beneath the Pterygoideus externus, medial to and in front of the inferior alveolar nerve, and is occasionally joined to this nerve by a branch which may cross the internal maxillary artery. The chorda tympani also joins it at an acute angle in this situation. The nerve then passes between the Pterygoideus internus and the ramus of the mandible, and crosses obliquely to the side of the tongue over the Constrictor pharyngis superior and Styloglossus, and then between the Hyoglos-sus and deep part of the submaxillary gland; it finally runs across the duct of the submaxillary gland, and along the tongue to its tip, lying immediately beneath the mucous membrane.

Its branches of communication are with the facial (through the chorda tympani), the inferior alveolar and hy-poglossal nerves, and the submaxillary ganglion. The branches to the submaxillary ganglion are two or three in number; those connected with the hypoglossal nerve form a plexus at the anterior margin of the Hyoglossus.

Its branches of distribution supply the sublingual gland, the mucous membrane of the mouth, the gums, and the mucous membrane of the anterior two-thirds of the tongue; the terminal filaments communicate, at the tip of the tongue, with the hypoglossal nerve.

The Inferior Alveolar Nerve (n. alveolaris inferior; inferior dental nerve) is the largest branch of the mandibular nerve. It descends with the inferior alveolar artery, at first beneath the Pterygoideus externus, and then between the spheno-mandibular ligament and the ramus of the mandible to the mandibular foramen. It then passes forward in the mandibular canal, beneath the teeth, as far as the mental foramen, where it divides into two terminal branches, incisive and mental.

The branches of the inferior alveolar nerve are the mylohyoid, dental, incisive, and mental.The mylohyoid nerve (n. mylohyoideus) is derived from the inferior alveolar just before it enters the mandibular

foramen. It descends in a groove on the deep surface of the ramus of the mandible, and reaching the under surface of the Mylohyoideus supplies this muscle and the anterior belly of the Digastricus.

The dental branches supply the molar and premolar teeth. They correspond in number to the roots of those teeth; each nerve entering the orifice at the point of the root, and supplying the pulp of the tooth; above the alveolar nerve they form an inferior dental plexus.

The incisive branch is continued onward within the bone, and supplies the canine and incisor teeth.The mental nerve (n. mentalis) emerges at the mental foramen, and divides beneath the Triangularis muscle into

three branches; one descends to the skin of the chin, and two ascend to the skin and mucous membrane of the lower lip; these branches communicate freely with the facial nerve.

Two small ganglia, the otic and the submaxillary, are connected with the mandibular nerve.Otic Ganglion (ganglion oticum).—The otic ganglion is a small, ovalshaped, flattened ganglion of a reddish-gray

color, situated immediately below the foramen ovale; it lies on the medial surface of the mandibular nerve, and surrounds the origin of the nerve to the Pterygoideus internus. It is in relation, laterally, with the trunk of the mandibular nerve at the point where the motor and sensory roots join; medially, with the cartilaginous part of the auditory tube, and the origin of the Tensor veli palatini; posteriorly, with the middle meningeal artery.

Branches of Communication.—It is connected by two or three short filaments with the nerve to the Pterygoideus internus, from which it may obtain a motor, and possibly a sensory root. It communicates with the glossopharyngeal and fa-cial nerves, through the lesser superficial petrosal nerve continued from the tympanic plexus, and through this nerve it probably receives a root from the glossopharyngeal and a motor root from the facial; its sympathetic root consists of a fila-ment from the plexus surrounding the middle meningeal artery. The fibers from the glossopharyngeal which pass to the otic ganglion in the small superficial petrosal are supposed to be sympathetic efferent (preganglionic) fibers from the dorsal nu -cleus or inferior salivatory nucleus of the medulla. Fibers (postganglionic) from the otic ganglion with which these form synapses are supposed to pass with the auriculotemporal nerve to the parotid gland. A slender filament (sphenoidal) as-cends from it to the nerve of the Pterygoid canal, and a small branch connects it with the chorda tympani.

Its branches of distribution are: a filament to the Tensor tympani, and one to the Tensor veli palatini. The former passes backward, lateral to the auditory tube; the latter arises from the ganglion, near the origin of the nerve to the Ptery -goideus internus, and is directed forward. The fibers of these nerves are, however, mainly derived from the nerve to the Pterygoideus internus.

Submaxillary Ganglion (ganglion submaxillare).—The submaxillary ganglion is of small size and is fusiform in shape. It is situated above the deep portion of the submaxillary gland, on the hyoglossus, near the posterior border of the Mylohyoideus, and is connected by filaments with the lower border of the lingual nerve. It is suspended from the lingual nerve by two filaments which join the anterior and posterior parts of the ganglion. Through the posterior of these it receives a branch from the chorda tympani nerve which runs in the sheath of the lingual; these are sympathetic efferent (pregan -glionic) fibers from the facial nucleus or the superior salivatory nucleus of the medulla oblongata that terminate in the sub-maxillary ganglion. The postganglionic fibers pass to the submaxillary gland, it communicates with the sympathetic by fila -ments from the sympathetic plexus around the external maxillary artery.

Its branches of distribution are five or six in number; they arise from the lower part of the ganglion, and supply the mucous membrane of the mouth and the duct of the submaxillary gland, some being lost in the submaxillary gland. The branch of communication from the lingual to the forepart of the ganglion is by some regarded as a branch of distribution, through which filaments pass from the ganglion to the lingual nerve, and by it are conveyed to the sublingual gland and the tongue.

Trigeminal Nerve Reflexes.—Pains referred to various branches of the trigeminal nerve are of very frequent occur-rence, and should always lead to a careful examination in order to discover a local cause. As a general rule the diffusion of pain over the various branches of the nerve is at first confined to one only of the main divisions, and the search for the causative lesion should always commence with a thorough examination of all those parts which are supplied by that divi-sion; although in severe cases pain may radiate over the branches of the other main divisions. The commonest example of this condition is the neuralgia which is so often associated with dental caries—here, although the tooth itself may not ap -pear to be painful, the most distressing referred pains may be experienced, and these are at once relieved by treatment di -rected to the affected tooth.

Many other examples of trigeminal reflexes could be quoted, but it will be sufficient to mention the more common ones. Dealing with the ophthalmic nerve, severe supraorbital pain is commonly associated with acute glaucoma or with dis -ease of the frontal or ethmoidal air cells. Malignant growths or empyema of the maxillary antrum, or unhealthy conditions about the inferior conchae or the septum of the nose, are often found giving rise to “second division” neuralgia, and should be always looked for in the absence of dental disease in the maxilla.

It is on the mandibular nerve, however, that some of the most striking reflexes are seen. It is quite common to meet with patients who complain of pain in the ear, in whom there is no sign of aural disease, and the cause is usually to be found in a carious tooth in the mandible. Moreover, with an ulcer or cancer of the tongue, often the first pain to be experi -enced is one which radiates to the ear and temporal fossa, over the distribution of the auriculotemporal nerve.

Note. After it enters the infraorbital canal, the nerve is frequently called the infraorbital.

Practice skillsStudents are supposed to identify the following structures on the samples:

Trigeminal nerve (V pair) and its ganglion- ophthalmic nerve (1 branch of V pair)- maxillary nerve (2 branch of V pair) - mandibular nerve (3 branch of V pair)

- auriculotemporal nerve- lingual nerve- inferior alveolar nerve

Practice class 10. The facial nerve (VIІ). The glossopharyngeal (ІХ) nerve.

The aim: to learn the facial and glossopharyngeal nerves, their branches and objects of innervation.Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-

sents special interest for therapists, neurologists, neuropathologists and others.The plan of the practice class:

A. Checking of the home assignment: oral quiz or written test control – 30 minutes.B. Summary lecture on the topic by teacher – 30 minutes.

a) The general characteristic if the facial nerve, its nuclei; roots and ganglion.b) The branches of communication of the facial nerve.c) The branches of distribution of the facial nerve.d) The glossopharyngeal nerve.

C. Students’ self-taught time – 55 minutesD. Home-task – 5 minutes

The Facial Nerve (N. Facialis; Seventh Nerve)The facial nerve consists of a motor and a sensory part, the latter being frequently described under the name of the

nervus intermedius (pars intermedii of Wrisberg). The two parts emerge at the lower border of the pons in the recess be-tween the olive and the inferior peduncle, the motor part being the more medial, immediately to the lateral side of the sen-sory part is the acoustic nerve.

The motor part supplies somatic motor fibers to the muscles of the face, scalp, and auricle, the Buccinator and Platysma, the Stapedius, the Stylohyoideus, and posterior belly of the Digastricus; it also contains some sympathetic motor fibers which constitute the vasodilator nerves of the submaxillary and sublingual glands, and are conveyed through the chorda tympani nerve. These are preganglionic fibers of the sympathetic system and terminate in the submaxillary ganglion and small ganglia in the hilus of the submaxillary gland. From these ganglia postganglionic fibers are conveyed to these glands. The sensory part contains the fibers of taste for the anterior two-thirds of the tongue and a few somatic sensory fibers from the middle ear region. A few splanchnic sensory fibers are also present.

The motor root arises from a nucleus which lies deeply in the reticular formation of the lower part of the pons. This nucleus is situated above the nucleus ambiguus, behind the superior olivary nucleus, and medial to the spinal tract of the trigeminal nerve. From this origin the fibers pursue a curved course in the substance of the pons. They first pass backward and medialward toward the rhomboid fossa, and, reaching the posterior end of the nucleus of the abducent nerve, run up -ward close to the middle line beneath the colliculus fasciculus. At the anterior end of the nucleus of the abducent nerve they make a second bend, and run downward and forward through the pons to their point of emergence between the olive and the inferior peduncle.

The sensory root arises from the genicular ganglion, which is situated on the geniculum of the facial nerve in the facial canal, behind the hiatus of the canal. The cells of this ganglion are unipolar, and the single process divides in a T-shaped manner into central and peripheral branches. The central branches leave the trunk of the facial nerve in the internal acoustic meatus, and form the sensory root; the peripheral branches are continued into the chorda tympani and greater su -perficial petrosal nerves. Entering the brain at the lower border of the pons between the motor root and the acoustic nerve, the fibers of the sensory root pass into the substance of the medulla oblongata and end in the upper part of the terminal nu-cleus of the glossopharyngeal nerve and in the fasciculus solitarius

From their superficial attachments to the brain, the two roots of the facial nerve pass lateralward and forward with the acoustic nerve to the internal acoustic meatus. In the meatus the motor root lies in a groove on the upper and anterior surface of the acoustic nerve, the sensory root being placed between them.

At the bottom of the meatus, the facial nerve enters the facial canal, which it traverses to its termination at the stylo -mastoid foramen. It is at first directed lateralward between the cochlea and vestibule toward the medial wall of the tym-panic cavity; it then bends suddenly backward and arches downward behind the tympanic cavity to the stylomastoid fora-men. The point where it changes its direction is named the geniculum; it presents a reddish gangliform swelling, the genic-ular ganglion (ganglion geniculi; geniculate ganglion; nucleus of the sensory root of the nerve). On emerging from the stylomastoid foramen, the facial nerve runs forward in the substance of the parotid gland, crosses the external carotid artery, and divides behind the ramus of the mandible into branches, from which numerous offsets are distributed over the side of the head, face, and upper part of the neck, supplying the superficial muscles in these regions. The branches and their offsets unite to form the parotid plexus.

Branches of Communication.—The branches of communication of the facial nerve may be arranged as follows:

In the internal acoustic meatus - with the acoustic nerve; at the genicular ganglion; with the sphenopalatine ganglion by the greater superficial petrosal nerve; with the otic ganglion by a branch which joins the lesser superficial petrosal nerve; with the sympathetic on the middle meningeal artery.

In the facial canal - with the auricular branch of the vagus; at its exit from the stylomastoid foramen; with the glos -sopharyngeal; with the vagus; with the great auricular; with the auriculotemporal.

Behind the ear - with the lesser occipital.On the face - with the trigeminal.In the neck - with the cutaneous cervical.In the internal acoustic meatus some minute filaments pass from the facial to the acoustic nerve.The greater superficial petrosal nerve (large superficial petrosal nerve) arises from the genicular ganglion, and

consists chiefly of sensory branches which are distributed to the mucous membrane of the soft palate; but it probably con-tains a few motor fibers which form the motor root of the sphenopalatine ganglion. It passes forward through the hiatus of the facial canal, and runs in a sulcus on the anterior surface of the petrous portion of the temporal bone beneath the semilu -nar ganglion, to the foramen lacerum. It receives a twig from the tympanic plexus, and in the foramen is joined by the deep petrosal, from the sympathetic plexus on the internal carotid artery, to form the nerve of the pterygoid canal which passes forward through the pterygoid canal and ends in the sphenopalatine ganglion. The genicular ganglion is connected with the otic ganglion by a branch which joins the lesser superficial petrosal nerve, and also with the sympathetic filaments accom-panying the middle meningeal artery. According to Arnold, a twig passes back from the ganglion to the acoustic nerve. Just before the facial nerve emerges from the stylomastoid foramen, it generally receives a twig from the auricular branch of the vagus.

After its exit from the stylomastoid foramen, the facial nerve sends a twig to the glossopharyngeal, and communi-cates with the auricular branch of the vagus, with the great auricular nerve of the cervical plexus, with the auriculotemporal nerve in the parotid gland, and with the lesser occipital behind the ear; on the face with the terminal branches of the trigem -inal, and in the neck with the cutaneous cervical nerve.

Branches of Distribution.—The branches of distribution of the facial nerve may be thus arranged:With the facial canal - nerve to the Stapedius muscle; chorda tympani.At its exit from the stylomastoid foramen - Posterior auricular; Digastric; Stylohyoid.On the face – Temporal; Zygomatic; Buccal ; Mandibular; Cervical.The Nerve to the Stapedius (n. stapedius; tympanic branch) arises opposite the pyramidal eminence; it passes

through a small canal in this eminence to reach the muscle.The Chorda Tympani Nerve is given off from the facial as it passes downward behind the tympanic cavity, about 6

mm. from the stylomastoid foramen. It runs upward and forward in a canal, and enters the tympanic cavity, through an aperture (iter chordae posterius) on its posterior wall, close to the medial surface of the posterior border of the tympanic membrane and on a level with the upper end of the manubrium of the malleus. It traverses the tympanic cavity, between the fibrous and mucous layers of the tympanic membrane, crosses the manubrium of the malleus, and emerges from the cavity through a foramen situated at the inner end of the petrotympanic fissure, and named the iter chordae anterius (canal of Huguier). It then descends between the Pterygoideus externus and internus on the medial surface of the spina angularis of the sphenoid, which it sometimes grooves, and joins, at an acute angle, the posterior border of the lingual nerve. It receives a few efferent fibers from the motor root; these enter the submaxillary ganglion, and through it are distributed to the sub -maxillary and sublingual glands; the majority of its fibers are afferent, and are continued onward through the muscular sub-stance of the tongue to the mucous membrane covering its anterior two-thirds; they constitute the nerve of taste for this por-tion of the tongue. Before uniting with the lingual nerve the chorda tympani is joined by a small branch from the otic gan-glion.

The Posterior Auricular Nerve (n. auricularis posterior) arises close to the stylo-mastoid foramen, and runs up-ward in front of the mastoid process; here it is joined by a filament from the auricular branch of the vagus, and communi -cates with the posterior branch of the great auricular, and with the lesser occipital. As it ascends between the external acoustic meatus and mastoid process it divides into auricular and occipital branches. The auricular branch supplies the Auricularis posterior and the intrinsic muscles on the cranial surface of the auricula. The occipital branch, the larger, passes backward along the superior nuchal line of the occipital bone, and supplies the Occipitalis.

The Digastric Branch (ramus digastricus) arises close to the stylomastoid foramen, and divides into several fila-ments, which supply the posterior belly of the Digastricus; one of these filaments joins the glossopharyngeal nerve.

The Stylohyoid Branch (ramus stylohyoideus) frequently arises in conjunction with the digastric branch; it is long and slender, and enters the Stylohyoideus about its middle.

The Temporal Branches (rami temporales) cross the zygomatic arch to the temporal region, supplying the Auricu-lares anterior and superior, and joining with the zygomaticotemporal branch of the maxillary, and with the auriculotemporal branch of the mandibular. The more anterior branches supply the Frontalis, the Orbicularis oculi, and the Corrugator, and join the supraorbital and lacrimal branches of the ophthalmic.

The Zygomatic Branches (rami zygomatici; malar branches) run across the zygomatic bone to the lateral angle of the orbit, where they supply the Orbicularis oculi, and join with filaments from the lacrimal nerve and the zygomaticofacial branch of the maxillary nerve.

The Buccal Branches (rami buccales; infraorbital branches), of larger size than the rest, pass horizontally forward to be distributed below the orbit and around the mouth. The superficial branches run beneath the skin and above the su-perficial muscles of the face, which they supply: some are distributed to the Procerus, joining at the medial angle of the or -bit with the infratrochlear and nasociliary branches of the ophthalmic. The deep branches pass beneath the Zygomaticus and the Quadratus labii superioris, supplying them and forming an infraorbital plexus with the infraorbital branch of the

maxillary nerve. These branches also supply the small muscles of the nose. The lower deep branches supply the Buccinator and Orbicularis oris, and join with filaments of the buccinator branch of the mandibular nerve.

The Mandibular Branch (ramus marginalis mandibulae) passes forward beneath the Platysma and Triangularis, supplying the muscles of the lower lip and chin, and communicating with the mental branch of the inferior alveolar nerve.

The Cervical Branch (ramus colli) runs forward beneath the Platysma, and forms a series of arches across the side of the neck over the suprahyoid region. One branch descends to join the cervical cutaneous nerve from the cervical plexus; others supply the Platysma.

The Glossopharyngeal Nerve (IX cranial) is similar to the vagus nerve as regards its central connections and is usually described with it. It contains somatic sensory, sympathetic afferent, taste, somatic motor and sympathetic efferent fibers. The afferent sensory fibers arise from cells in the superior ganglion and in the petrosal ganglion. The same uncer-tainty exists concerning the nuclei of termination and nuclei of origin of the various components as for the vagus.

(1) The somatic sensory fibers are few in number. Some are distributed with the auricular branch of the vagus to the external ear; others probably pass to the pharynx and fauces. They are supposed to join the spinal tract of the trigeminal and terminate in its nucleus. The connections are similar to those of the somatic sensory fibers of the vagus.

(2) Sympathetic afferent fibers from the pharynx and middle ear are supposed to terminate in the dorsal nucleus. Connections are probably established with motor nuclei concerned in chewing and swallowing; very little is known, how -ever, about the connections with other parts of the brain.

(3) Taste fibers from the tongue probably terminate in the nucleus of the tractus solitarius. These fibers together with similar fibers from the facial (nervus intermedius) and the vagus are supposed to form the tractus solitarius and termi-nate in its nucleus. The central connections have been considered under the vagus.

(4) Somatic motor fibers to the Sylopharyngeus muscle arise in the upper end of the nucleus ambiguus. The exis -tence of these fibers in the roots of the glossopharyngeal is uncertain, as there are other paths by which such fibers might reach the glossopharyngeal from the vagus. The sources of impulses passing to the nucleus ambiguus are considered under the vagus.

(5) Sympathetic efferent fibers (motor and secretory fibers) arise from the nucleus dorsalis. Some authors believe that the secretory fibers to the parotid gland arise from a distinct nucleus, the inferior salivatory nucleus, situated near the dorsal nucleus. The preganglionic fibers from this nucleus terminate in the otic ganglion; the postganglionic fibers from the otic ganglion pass to the parotid gland.

Practice skillsStudents are supposed to identify the following structures on the samples:

facial and intermediate nerves (VII pair) glossopharyngeal nerve (IX pair)

Practice class 11. The vagus nerve (Х). The parasympathetic nervous system.

The aim: to learn the vagus nerve, its branches and objects of innervation; to learn the parasympathetic nervous system, its differences from the sympathetic one.

Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-sents special interest for therapists, neurologists, neuropathologists and others.

The plan of the practice class:A. Checking of the home assignment: oral quiz or written test control – 30 minutes.B. Summary lecture on the topic by teacher – 30 minutes.

a) The general characteristic of the vagus nerve, its nuclei and ganglia.b) The branches of the vagus nerve.c) The characteristic if the parasympathetic nervous system.

C. Students’ self-taught time – 55 minutesD. Home-task – 5 minutes

The Vagus Nerve (N. Vagus; Tenth Nerve; Pneumogastric Nerve)The vagus nerve is composed of both motor and sensory fibers, and has a more extensive course and distribution

than any of the other cranial nerves, since it passes through the neck and thorax to the abdomen.The vagus is attached by eight or ten filaments to the medulla oblongata in the groove between the olive and the in -

ferior peduncle, below the glossopharyngeal. The sensory fibers arise from the cells of the jugular ganglion and ganglion nodosum of the nerve, and, when traced into the medulla oblongata mostly end by arborizing around the cells of the inferior part of a nucleus which lies beneath the ala cinerea in the lower part of the rhomboid fossa. These are the sympathetic affer-ent fibers. Some of the sensory fibers of the glossopharyngeal nerve have been seen to end in the upper part of this nucleus. A few of the sensory fibers of the vagus, probably taste fibers, descend in the fasciculus solitarius and end around its cells. The somatic sensory fibers, few in number, from the posterior part of the external auditory meatus and the back of the ear, probably join the spinal tract of the trigeminal as it descends in the medulla. The somatic motor fibers arise from the cells of the nucleus ambiguus, already referred to in connection with the motor root of the glossopharyngeal nerve.

The sympathetic efferent fibers, distributed probably as preganglionic fibers to the thoracic and abdominal viscera, i. e., as motor fibers to the bronchial tree, inhibitory fibers to the heart, motor fibers to the esophagus, stomach, small intes-tine and gall passages, and as secretory fibers to the stomach and pancreas, arise from the dorsal nucleus of the vagus.

The filaments of the nerve unite, and form a flat cord, which passes beneath the flocculus to the jugular foramen, through which it leaves the cranium. In emerging through this opening, the vagus is accompanied by and contained in the same sheath of dura mater with the accessory nerve, a septum separating them from the glossopharyngeal which lies in front. In this situation the vagus presents a well-marked ganglionic enlargement, which is called the jugular ganglion (ganglion of the root); to it the accessory nerve is connected by one or two filaments. After its exit from the jugular fora -men the vagus is joined by the cranial portion of the accessory nerve, and enlarges into a second gangliform swelling, called the ganglion nodosum (ganglion of the trunk); through this the fibers of the cranial portion of the accessory pass without interruption, being principally distributed to the pharyngeal and superior laryngeal branches of the vagus, but some of its fibers descend in the trunk of the vagus, to be distributed with the recurrent nerve and probably also with the cardiac nerves.

The vagus nerve passes vertically down the neck within the carotid sheath, lying between the internal jugular vein and internal carotid artery as far as the upper border of the thyroid cartilage, and then between the same vein and the com -mon carotid artery to the root of the neck. The further course of the nerve differs on the two sides of the body.

On the right side, the nerve passes across the subclavian artery between it and the right innominate vein, and de-scends by the side of the trachea to the back of the root of the lung, where it spreads out in the posterior pulmonary plexus. From the lower part of this plexus two cords descend on the esophagus, and divide to form, with branches from the opposite nerve, the esophageal plexus. Below, these branches are collected into a single cord, which runs along the back of the esophagus enters the abdomen, and is distributed to the postero-inferior surface of the stomach, joining the left side of the celiac plexus, and sending filaments to the lienal plexus.

On the left side, the vagus enters the thorax between the left carotid and subclavian arteries, behind the left innomi-nate vein. It crosses the left side of the arch of the aorta, and descends behind the root of the left lung, forming there the posterior pulmonary plexus. From this it runs along the anterior surface of the esophagus, where it unites with the nerve of the right side in the esophageal plexus, and is continued to the stomach, distributing branches over its anterosuperior surface; some of these extend over the fundus, and others along the lesser curvature. Filaments from these branches enter the lesser omentum, and join the hepatic plexus.

The Jugular Ganglion (ganglion jugulare; ganglion of the root) is of a grayish color, spherical in form, about 4 mm. in diameter.

Branches of Communication.—This ganglion is connected by several delicate filaments to the cranial portion of the accessory nerve; it also communicates by a twig with the petrous ganglion of the glossopharyngeal, with the facial nerve by means of its auricular branch, and with the sympathetic by means of an ascending filament from the superior cer -vical ganglion.

The Ganglion Nodosum (ganglion of the trunk; inferior ganglion) is cylindrical in form, of a reddish color, and 2.5 cm. in length. Passing through it is the cranial portion of the accessory nerve, which blends with the vagus below the gan -glion.

Branches of Communication.—This ganglion is connected with the hypoglossal, the superior cervical ganglion of the sympathetic, and the loop between the first and second cervical nerves.

Branches of Distribution.—The branches of distribution of the vagus are:In the Jugular Fossa – Meningeal; Auricular.In the Neck – Pharyngeal; Superior laryngeal; Recurrent; Superior cardiac.In the Thorax - Inferior cardiac; Anterior bronchial; Posterior bronchial; Esophageal.In the Abdomen – Gastric; Celiac; Hepatic.The Meningeal Branch (ramus meningeus; dural branch) is a recurrent filament given off from the jugular gan-

glion; it is distributed to the dura mater in the posterior fossa of the base of the skull.The Auricular Branch (ramus auricularis; nerve of Arnold) arises from the jugular ganglion, and is joined soon af-

ter its origin by a filament from the petrous ganglion of the glossopharyngeal; it passes behind the internal jugular vein, and enters the mastoid canaliculus on the lateral wall of the jugular fossa. Traversing the substance of the temporal bone, it crosses the facial canal about 4 mm. above the stylomastoid foramen, and here it gives off an ascending branch which joins the facial nerve. The nerve reaches the surface by passing through the tympanomastoid fissure between the mastoid process and the tympanic part of the temporal bone, and divides into two branches: one joins the posterior auricular nerve, the other is distributed to the skin of the back of the auricula and to the posterior part of the external acoustic meatus.

The Pharyngeal Branch (ramus pharyngeus), the principal motor nerve of the pharynx, arises from the upper part of the ganglion nodosum, and consists principally of filaments from the cranial portion of the accessory nerve. It passes across the internal carotid artery to the upper border of the Constrictor pharyngis medius, where it divides into numerous filaments, which join with branches from the glossopharyngeal, sympathetic, and external laryngeal to form the pharyn-geal plexus. From the plexus, branches are distributed to the muscles and mucous membrane of the pharynx and the mus-cles of the soft palate, except the Tensor veli palatini. A minute filament descends and joins the hypoglossal nerve as it winds around the occipital artery.

The Superior Laryngeal Nerve (n. laryngeus superior) larger than the preceding, arises from the middle of the ganglion nodosum and in its course receives a branch from the superior cervical ganglion of the sympathetic. It descends, by the side of the pharynx, behind the internal carotid artery, and divides into two branches, external and internal.

The external branch (ramus externus), the smaller, descends on the larynx, beneath the Sternothyreoideus, to sup-ply the Cricothyreoideus. It gives branches to the pharyngeal plexus and the Constrictor pharyngis inferior, and communi-

cates with the superior cardiac nerve, behind the common carotid artery.The internal branch (ramus internus) descends to the hyothyroid membrane, pierces it in company with the supe-

rior laryngeal artery, and is distributed to the mucous membrane of the larynx. Of these branches some are distributed to the epiglottis, the base of the tongue, and the epiglottic glands; others pass backward, in the aryepiglottic fold, to supply the mucous membrane surrounding the entrance of the larynx, and that lining the cavity of the larynx as low down as the vocal folds. A filament descends beneath the mucous membrane on the inner surface of the thyroid cartilage and joins the recur -rent nerve.

The Recurrent Nerve (n. recurrens; inferior or recurrent laryngeal nerve) arises, on the right side, in front of the subclavian artery; winds from before backward around that vessel, and ascends obliquely to the side of the trachea behind the common carotid artery, and either in front of or behind the inferior thyroid artery. On the left side, it arises on the left of the arch of the aorta, and winds below the aorta at the point where the ligamentum arteriosum is attached, and then ascends to the side of the trachea. The nerve on either side ascends in the groove between the trachea and esophagus, passes under the lower border of the Constrictor pharyngis inferior, and enters the larynx behind the articulation of the inferior cornu of the thyroid cartilage with the cricoid; it is distributed to all the muscles of the larynx, excepting the Cricothyreoideus. It communicates with the internal branch of the superior laryngeal nerve, and gives off a few filaments to the mucous mem-brane of the lower part of the larynx.

As the recurrent nerve hooks around the subclavian artery or aorta, it gives off several cardiac filaments to the deep part of the cardiac plexus. As it ascends in the neck it gives off branches, more numerous on the left than on the right side, to the mucous membrane and muscular coat of the esophagus; branches to the mucous membrane and muscular fibers of the trachea; and some pharyngeal filaments to the Constrictor pharyngis inferior.

The Superior Cardiac Branches (rami cardiaci superiores; cervical cardiac branches), two or three in number, arise from the vagus, at the upper and lower parts of the neck.

The upper branches are small, and communicate with the cardiac branches of the sympathetic. They can be traced to the deep part of the cardiac plexus.

The lower branch arises at the root of the neck, just above the first rib. That from the right vagus passes in front or by the side of the innominate artery, and proceeds to the deep part of the cardiac plexus; that from the left runs down across the left side of the arch of the aorta, and joins the superficial part of the cardiac plexus.

The Inferior Cardiac Branches (rami cardiaci inferiores; thoracic cardiac branches), on the right side, arise from the trunk of the vagus as it lies by the side of the trachea, and from its recurrent nerve; on the left side from the recurrent nerve only; passing inward, they end in the deep part of the cardiac plexus.

The Anterior Bronchial Branches (rami bronchiales anteriores; anterior or ventral pulmonary branches), two or three in number, and of small size, are distributed on the anterior surface of the root of the lung. They join with filaments from the sympathetic, and form the anterior pulmonary plexus.

The Posterior Bronchial Branches (rami bronchiales posteriores; posterior or dorsal pulmonary branches), more numerous and larger than the anterior, are distributed on the posterior surface of the root of the lung; they are joined by fila-ments from the third and fourth (sometimes also from the first and second) thoracic ganglia of the sympathetic trunk, and form the posterior pulmonary plexus. Branches from this plexus accompany the ramifications of the bronchi through the substance of the lung.

The Esophageal Branches (rami aesophagei) are given off both above and below the bronchial branches; the lower are numerous and larger than the upper. They form, together with the branches from the opposite nerve, the esophageal plexus. From this plexus filaments are distributed to the back of the pericardium.

The Gastric Branches (rami gastrici) are distributed to the stomach. The right vagus forms the posterior gastric plexus on the postero-inferior surface of the stomach and the left the anterior gastric plexus on the antero-superior sur-face.

The Celiac Branches (rami caeliaci) are mainly derived from the right vagus: they join the celiac plexus and through it supply branches to the pancreas, spleen, kidneys, suprarenal bodies, and intestine.

The Hepatic Branches (rami hepatici) arise from the left vagus: they join the hepatic plexus and through it are con-veyed to the liver.

Parasympathetic system. The fibers of the central parasympathetic neurons pass to parasympathetic ganglia in the head region in various cranial nerves. There a relay takes place to postganglionic fibers, which innervate the effector organ The vagus, as the principal nerve of the parasympathetic system, descends together with the large cervical vessels (neurovascu-lar trunk of the neck) and, after passing through the superior aperture of the thorax, it divides into a plexus in the region of the thoracic and abdominal viscera.Cells situated in the intermediolateral nucleus and the intermediomedial nucleus of the sacral cord send their axons through the 3rd and 4th sacral nerves, to the pudendal nerve from which they pass as the pelvic nerves into the inferior hypogastric plexus and to the pelvic organs (bladder, rectum and genitalia) Synapses with postganglionic fibers are found in the inferior hypogastric plexus, or in small ganglia in the various organ plexuses

The Cranial Parasympathetics—The cranial parasympathetics include parasympathetic efferent fibers in the oculomotor, facial, glossopharyngeal and vagus nerves, as well as parasympathetic afferent in the last three nerves.

The Oculomotor Nerve (III cranial) contains somatic motor fibers to the Obliquus inferior, Rectus inferior, Rectus superior, Levator palpebrae superioris and Rectus medialis muscles and parasympathetic efferent fibers (preganglionic fibers) to the ciliary ganglion. The postganglionic fibers connected with these supply the ciliary muscle and the sphincter of the iris. The axons arise from the nucleus of the oculomotor nerve and pass in bundles through the posterior longitudinal

bundle, the tegmentum, the red nucleus and the medial margin of the substantia nigra in a series of curves and finally emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.

The Parasympathetic Efferent Fibers of the Oculomotor Nerve probably arise from cells in the anterior part of the oculomotor nucleus which is located in the tegmentum of the mid-brain. These preganglionic fibers run with the third nerve into the orbit and pass to the ciliary ganglion where they terminate by forming synapses with parasympathetic motor neurons whose axons, postganglionic fibers, proceed as the short ciliary nerves to the eyeball. Here they supply motor fibers to the Ciliaris muscle and the Sphincter pupillae muscle. So far as known there are no parasympathetic afferent fibers connected with the nerve.

The oculomotor nucleus lies in the gray substance of the floor of the cerebral aqueduct subjacent to the superior colliculus and extends in front of the aqueduct a short distance into the floor of the third ventricle. The inferior end is con -tinuous with the trochlear nucleus. It is from 6 to 10 mm. in length. It is intimately related to the posterior longitudinal bun -dle which lies against its ventro-lateral aspect and many of its cells lie among the fibers of the posterior longitudinal bun-dle. The nucleus of the oculomotor nerve contains several distinct groups of cells which differ in size and appearance from each other and are supposed to send their axons each to a separate muscle. Much uncertainty still exists as to which group supplies which muscle. There are seven of these groups or nuclei on either side of the midline and one medial nucleus. The cells of the anterior nuclei are smaller and are supposed to give off the parasympathetic efferent axons. The majority of fibers arise from the nucleus of the same side some, however, cross from the opposite side and are supposed to supply the Rectus medialis muscle. Since oculomotor and abducens nuclei are intimately connected by the posterior longitudinal bun-dle this decussation of fibers to the Medial rectus may facilitate the conjugate movements of the eyes in which the Medial and Lateral recti are especially involved.

Many collaterals and terminals are given off to the oculomotor nucleus from the posterior longitudinal bundle and thus connect it with the vestibular nucleus, the trochlear and abducens nuclei and probably with other cranial nuclei. Fibers from the visual reflex center in the superior colliculus pass to the nucleus. It is also connected with the cortex of the occipi -tal lobe of the cerebrum by fibers which pass through the optic radiation. The pathway for voluntary motor impulses is probably similar to that for the abducent nerve.

The Facial Nerve.The Parasympathetic Efferent Fibers of the Facial Nerve are supposed to arise from the small cells of the facial

nucleus. According to some authors the fibers to the salivary glands arise from a special nucleus, the superior salivatory nu -cleus, consisting of cells scattered in the reticular formation, dorso-medial to the facial nucleus. These preganglionic fibers are distributed partly through the chorda tympani and lingual nerves to the submaxillary ganglion where they terminate about the cell bodies of neurons whose axons as postganglionic fibers conduct secretory and vasodilotar impulses to the submaxillary and sublingual glands. Other preganglionic fibers of the facial nerve pass via the great superficial petrosal nerve to the sphenopalatine ganglion where they form synapses with neurons whose postganglionic fibers are distributed with the superior maxillary nerve as vasodilator and secretory fibers to the mucous membrane of the nose, soft palate, ton -sils, uvula, roof of the mouth, upper lips and gums, parotid and orbital glands.

There are supposed to be a few parasympathetic afferent fibers connected with the facial nerve, whose cell bodies lie in the geniculate ganglion, but very little is known about them.

Parasympathetic efferent fibers (preganglionic fibers) arise according to some authors from the small cells of the fa-cial nucleus, or according to others from a special nucleus of cells scattered in the reticular formation, dorso-medial to the facial nucleus. This is sometimes called the superior salivatory nucleus. These preganglionic fibers are distributed partly via the chorda tympani and lingual nerves to the submaxillary ganglion, thence by postganglionic (vasodilator) fibers to the submaxillary and sublingual glands. Some of the preganglionic fibers pass to the sphenopalatine ganglion via the great su -perficial petrosal nerve.

The parasympathetic afferent fibers are likewise few in number and of unknown termination.The Glossopharyngeal Nerve.The Parasympathetic Afferent Fibers of the Glossopharyngeal Nerve are supposed to arise either in the dorsal

nucleus (nucleus ala cinerea) or in a distinct nucleus, the inferior salivatory nucleus, situated near the dorsal nucleus. These preganglionic fibers pass into the tympanic branch of the glossopharyngeal and then with the small superficial petrosal nerve to the otic ganglion. Postganglionic fibers, vasodilator and secretory fibers, are distributed to the parotid gland, to the mucous membrane and its glands on the tongue, the floor of the mouth, and the lower gums.

Parasympathetic Afferent Fibers, whose cells of origin lie in the superior or inferior ganglion of the trunk, are supposed to terminate in the dorsal nucleus. Very little is known of the peripheral distribution of these fibers.

Parasympathetic afferent fibers from the pharynx and middle ear are supposed to terminate in the dorsal nucleus. Connections are probably established with motor nuclei concerned in chewing and swallowing; very little is known, how -ever, about the connections with other parts of the brain.

Parasympathetic efferent fibers (motor and secretory fibers) arise from the nucleus dorsalis. Some authors believe that the secretory fibers to the parotid gland arise from a distinct nucleus, the inferior salivatory nucleus, situated near the dorsal nucleus. The preganglionic fibers from this nucleus terminate in the otic ganglion; the postganglionic fibers from the otic ganglion pass to the parotid gland.

The Vagus Nerve.Parasympathetic efferent fibers arise from cells in the dorsal nucleus (nucleus of the ala cinerea). These are pre-

ganglionic fibers of the parasympathetic system and all terminate in parasympathetic ganglia from which postganglionic fibers are distributed to various organs, i. e., motor fibers to the esophagus, stomach, small intestine, gallbladder, and to the lungs; inhibitory fibers to the heart; secretory fibers to the stomach and pancreas. The dorsal nucleus not only receives ter-

minals of parasympathetic afferent fibers for reflexes but undoubtedly receives terminals and collaterals from many other sources, but the exact pathways are at present unknown.

The Parasympathetic Efferent Fibers of the Vagus Nerve are supposed to arise in the dorsal nucleus (nucleus ala cinerea). These preganglionic fibers are all supposed to end in parasympathetic ganglia situated in or near the organs sup -plied by the vagus parasympathetics. The inhibitory fibers to the heart probably terminate in the small ganglia of the heart wall especially the atrium, from which inhibitory postganglionic fibers are distributed to the musculature. The pregan -glionic motor fibers to the esophagus, the stomach, the small intestine, and the greater part of the large intestine are sup-posed to terminate in the plexuses of Auerbach, from which postganglionic fibers are distributed to the smooth muscles of these organs. Other fibers pass to the smooth muscles of the bronchial tree and to the gall-bladder and its ducts. In addition the vagus is believed to contain secretory fibers to the stomach and pancreas. It probably contains many other efferent fibers than those enumerated above.

The parasympathetic afferent fibers are usually described as terminating in the dorsal nucleus of the vagus and glossopharyngeal. Some authors, however, believe they join the tractus solitarius and terminate in its nucleus. These affer -ent fibers convey impulses from the heart, the pancreas, and probably from the stomach, esophagus and respiratory tract. Their terminals in the dorsal nucleus come into relation with neurons whose axons probably descend into the spinal cord, conveying impulses to the motor nuclei supplying fibers to the muscles of respiration, i. e., the phrenic nerve and the nerves to the intercostal and levatores costarum muscles. Other axons probably convey vasomotor impulses to certain parasympa-thetic efferent neurons throughout the spinal cord. The dorsal nucleus (nucleus of the ala cinerea) and the posterior continu-ation of it into the commissural nucleus of the ala cinerea constitute probably the so-called respiratory and vaso-motor cen -ter of the medulla. The shorter reflex neurons of the dorsal nucleus probably effect connections either directly or indirectly with motor cells of the vagus itself and other cranial nerves.

Parasympathetic Afferent Fibers of the Vagus, whose cells of origin lie in the jugular ganglion or the ganglion no-dosum, probably terminate in the dorsal nucleus of the medulla oblongata or according to some authors in the nucleus of the tractus solitarius. Peripherally the fibers are supposed to be distributed to the various organs supplied by the parasympa-thetic efferent fibers.

The Sacral Parasympathetics—The Sacral Parasympathetic Efferent Fibers leave the spinal cord with the ante-rior roots of the second, third and fourth sacral nerves. These small medullated preganglionic fibers are collected together in the pelvis into the nervus erigentes or pelvic nerve which proceeds to the hypogastric or pelvic plexuses from which postganglionic fibers are distributed to the pelvic viscera. Motor fibers pass to the smooth muscle of the descending colon, rectum, anus and bladder. Vasodilators are distributed to these organs and to the external genitalia, while inhibitory fibers probably pass to the smooth muscles of the external genitalia. Afferent parasympathetic fibers conduct impulses from the pelvic viscera to the second, third and fourth sacral nerves. Their cells of origin lie in the spinal ganglia.

Practice skillsStudents are supposed to identify the following structures on the samples:

Vagus nerve (X pair) - recurrent laryngeal nerve

- anterior et posterior vagal trunks

Self-taught class 8. Review of the peripheral nervous system. Review of cranial nerves.

The aim: to learn the general characteristic of the peripheral nervous system and cranial nerves.Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-

sents special interest for therapists, neurologists, neuropathologists and others.The plan of the self-taught class:

A. Revise the division of the nervous system into the central and peripheral.B. Revise the general characteristic of spinal nerves.C. Revise the projection of cranial nerves’ nuclei on the dorsal surface of the brainstem and the places where

cranial nerves leave the brain.D. Learn the general characteristic of the cranial nerves.E. Compare the spinal and cranial nerves.F. Find out the connection of cranial nerves’ nuclei with other subcortical ganglia.

The cranial nerves.The cranial nerves are more varied in their composition than the spinal nerves. Some, for example, contain somatic

motor fibers only, others contain the various types of fibers found in the spinal nerves, namely, somatic motor, sympathetic efferent, somatic sensory and sympathetic sensory. In addition there are included the nerves of the special senses, namely, the nerves of smell, sight, hearing, equilibration and taste.

The Hypoglossal Nerve (XII cranial) consists of somatic motor fibers only and supplies the muscles of the tongue. Its axons arise from cells in the hypoglossal nucleus and pass forward between the white reticular formation and the gray reticular formation to emerge from the antero-lateral sulcus of the medulla. The hypoglossal nuclei of the two sides are con-nected by many commissural fibers and also by dendrites of motor cells which extend across the midline to the opposite nu-cleus. The hypoglossal nucleus receives either directly or indirectly numerous collaterals and terminals from the opposite pyramidal tract (cortico-bulbar or cerebrobulbar fibers) which convey voluntary motor impulses from the cerebral cortex.

Many reflex collaterals enter the nucleus from the secondary sensory paths of the trigeminal and vagus and probably also from the nervus intermedius and the glossopharyngeal. Collaterals from the posterior longitudinal bundle and the ventral longitudinal bundle are said to pass to the nucleus.

The Accessory Nerve (XI cranial) contains somatic motor fibers. The spinal part arises from lateral cell groups in the anterior column near its dorso-lateral margin in the upper five or six segments of the cord, its roots pass through the lat-eral funiculus to the lateral surface of the cord. It supplies the Trapezius and Sternocleidomastoideus. The cranial part arises from the nucleus ambiguus, the continuation in the medulla oblongata of the lateral cell groups of the anterior col -umn of the spinal cord from which the spinal part has origin. The upper part of the nucleus ambiguus gives motor fibers to the vagus and glossopharyngeal nerves. The cranial part sends it fibers through the vagus to the laryngeal nerves to supply the muscles of the larynx. The root fibers of the cranial part of the accessory nerve pass anterior to the spinal tract of the trigeminal while those of the vagus pass through or dorsal to the trigeminal root, and emerge in the line of the postero-lat -eral sulcus. The nucleus of origin of the spinal part undoubtedly receives either directly or indirectly terminals and collater -als controlling voluntary movements from the pyramidal tracts. It is probable that terminals and collaterals reach the nu -cleus either directly or indirectly from the rubrospinal and the vestibulospinal tracts. It is also connected indirectly with the spinal somatic sensory nerves by association fibers of the proper fasciculi. The cranial part receives indirectly or directly terminals and collaterals from the opposite pyramidal tract and form the terminal sensory nuclei of the cranial nerves. A few fibers of the cranial part are said to arise in the dorsal nucleus of the vagus and are thus sympathetic efferent. They are said to join the vagus nerve.

The Vagus Nerve (X cranial) contains somatic sensory, sympathetic afferent, somatic motor, sympathetic efferent and (taste fibers?). The afferent fibers (somatic sensory, sympathetic, and taste) have their cells of origin in the jugular gan -glion and in the nodosal ganglion (ganglion of the trunk) and on entering the medulla divide into ascending and descending branches as do the sensory fibers of the posterior roots of the spinal nerves after they enter the spinal cord.

(1) The somatic sensory fibers are few in number, convey impulses from a limited area of the skin on the back of the ear and posterior part of the external auditory meatus, and probably join the spinal tract of the trigeminal nerve to termi-nate in its nucleus. Connections are probably established through the central path of the trigeminal with the thalamus and somatic sensory area of the cortex for the conscious recognition of impulses. The descending fibers in the spinal tract of the trigeminal terminating in the nucleus of the tract probably establish relations through connecting neurons with motor nuclei in the anterior column of the spinal cord and with motor nuclei of the medulla.

(2) The sympathetic afferent fibers are usually described as terminating in the dorsal nucleus of the vagus and glossopharyngeal. Some authors, however, believe they join the tractus solitarius and terminate in its nucleus. These affer -ent fibers convey impulses from the heart, the pancreas, and probably from the stomach, esophagus and respiratory tract. Their terminals in the dorsal nucleus come into relation with neurons whose axons probably descend into the spinal cord, conveying impulses to the motor nuclei supplying fibers to the muscles of respiration, i. e., the phrenic nerve and the nerves to the intercostal and levatores costarum muscles. Other axons probably convey vasomotor impulses to certain sympathetic efferent neurons throughout the spinal cord. The dorsal nucleus (nucleus of the ala cinerea) and the posterior continuation of it into the commissural nucleus of the ala cinerea constitute probably the so-called respiratory and vaso-motor center of the medulla. The shorter reflex neurons of the dorsal nucleus probably effect connections either directly or indirectly with motor cells of the vagus itself and other cranial nerves.

(3) Taste fibers conducting impulses from the epiglottis and larynx are supposed to pass in the vagus and to join the tractus solitarius, finally terminating in the nucleus of the tractus solitarius. It is not certain that this nucleus represents the primary terminal center for taste and some authors maintain that the taste fibers terminate in the dorsal nucleus. The secondary ascending pathways from the primary gustatory nucleus to the cortex as well as the location of the cortical center for taste are unknown. A gustatory center has been described near the anterior end of the temporal lobe. The nucleus of the tractus solitarius is connected with motor centers of the pons, medulla and spinal cord for the reactions of mastication and swallowing.

(4) Somatic motor fibers to the cross striated muscles of the pharynx and larynx arise in the nucleus ambiguus. This nucleus undoubtedly receives either directly or indirectly collaterals or terminals from the opposite pyramidal tract controlling the voluntary movements of the pharynx and larynx. The reflex pathways conveying impulses from the terminal sensory nuclei are unknown, but probably form part of the intricate maze of fibers constituting the reticular formation.

(5) Sympathetic efferent fibers arise from cells in the dorsal nucleus (nucleus of the ala cinerea). These are pre-ganglionic fibers of the sympathetic system and all terminate in sympathetic ganglia from which postganglionic fibers are distributed to various organs, i. e., motor fibers to the esophagus, stomach, small intestine, gallbladder, and to the lungs; in-hibitory fibers to the heart; secretory fibers to the stomach and pancreas. The dorsal nucleus not only receives terminals of sympathetic afferent fibers for reflexes but undoubtedly receives terminals and collaterals from many other sources, but the exact pathways are at present unknown.

The Glossopharyngeal Nerve (IX cranial) is similar to the vagus nerve as regards its central connections and is usually described with it. It contains somatic sensory, sympathetic afferent, taste, somatic motor and sympathetic efferent fibers. The afferent sensory fibers arise from cells in the superior ganglion and in the petrosal ganglion. The same uncer-tainty exists concerning the nuclei of termination and nuclei of origin of the various components as for the vagus.

(1) The somatic sensory fibers are few in number. Some are distributed with the auricular branch of the vagus to the external ear; others probably pass to the pharynx and fauces. They are supposed to join the spinal tract of the trigeminal and terminate in its nucleus. The connections are similar to those of the somatic sensory fibers of the vagus.

(2) Sympathetic afferent fibers from the pharynx and middle ear are supposed to terminate in the dorsal nucleus. Connections are probably established with motor nuclei concerned in chewing and swallowing; very little is known, how -ever, about the connections with other parts of the brain.

(3) Taste fibers from the tongue probably terminate in the nucleus of the tractus solitarius. These fibers together with similar fibers from the facial (nervus intermedius) and the vagus are supposed to form the tractus solitarius and termi-nate in its nucleus. The central connections have been considered under the vagus.

(4) Somatic motor fibers to the Sylopharyngeus muscle arise in the upper end of the nucleus ambiguus. The exis-tence of these fibers in the roots of the glossopharyngeal is uncertain, as there are other paths by which such fibers might reach the glossopharyngeal from the vagus. The sources of impulses passing to the nucleus ambiguus are considered under the vagus.

(5) Sympathetic efferent fibers (motor and secretory fibers) arise from the nucleus dorsalis. Some authors believe that the secretory fibers to the parotid gland arise from a distinct nucleus, the inferior salivatory nucleus, situated near the dorsal nucleus. The preganglionic fibers from this nucleus terminate in the otic ganglion; the postganglionic fibers from the otic ganglion pass to the parotid gland.

The Acoustic Nerve (VIII cranial) consists of two distinct nerves the cochlear nerve, the nerve of hearing, and the vestibular nerve, the nerve of equilibration.

The Cochlear Nerve arises from bipolar cells in the spiral ganglion of the cochlea; the peripheral fibers end in the organ of Corti, the central fibers bifurcate as they enter the cochlear nucleus; the short ascending branches end in the ven-tral portion of the nucleus, the longer descending branches terminate in the dorsal portion of the nucleus. From the dorsal portion of the cochlear nucleus axons arise which pass across the dorsal aspect of the inferior peduncle and the floor of the fourth ventricle, the striae medullares, to the median sulcus. Here they dip into the substance of the pons, cross the median plane, and join the lateral lemniscus. Some of the fibers terminate in the superior olivary nucleus. The fibers of the striae medullares are not always visible on the floor of the rhomboid fossa. From the ventral portion of the cochlear nucleus ax-ons pass into the trapezoid body, here some of them end in the superior olivary nucleus of the same side, others cross the midline and end in the superior olivary nucleus of the opposite side or pass by these nuclei, giving off collaterals to them, and join the lateral lemniscus. Other fibers either terminate in or give off collaterals to the nucleus of the trapezoid body of the same or the opposite side. Other fibers from the ventral portion of the cochlear nucleus pass dorsal to the inferior pe -duncle and then dip into the substance of the pons to join the trapezoid body or the superior olivary nucleus of the same side. From the superior olivary nucleus of the same and opposite sides axons join the lateral lemniscus. Collaterals and probably terminals also pass from the lateral lemniscus to other nuclei in its path and receive in turn axons from these nu-clei. They are the accessory nucleus, the medial preolivary nucleus, the lateral preolivary or semilunar nucleus and the nu -cleus of the lateral lemniscus.

The trapezoid body consists of horizontal fibers in the ventral part of the formatio reticularis of the lower part of the pons behind its deep transverse fibers and the pyramid bundles. The axons come from the dorsal and ventral portions of the cochlear nucleus. After crossing the raphé, where they decussate with those from the opposite side, they turn upward to form the lateral lemniscus. Fibers from the striae medullares contribute to the trapezoid body, in addition it sends terminals or collaterals to and receives axons from the superior olivary nucleus, the nucleus of the trapezoid body, the lateral preoli -vary or semilunar nucleus and the mesial preolivary nucleus.

The cochlear nucleus, the terminal nucleus for the nerve of hearing, is usually described as consisting of a larger dorsal nucleus on the dorsal and lateral aspect of the inferior peduncle forming a prominent projection, the acoustic tuber-cle, and a ventral or accessory cochlear nucleus more ventral to the inferior peduncle. The two nuclei are continuous and are merely portions of one large nucleus. The axons from cells of the spiral ganglion of the cochlear nerve on reaching the nucleus divide into ascending and descending branches which enter the ventral and dorsal nuclei respectively. Axons from the large fusiform cells of the dorsal nucleus pass partly by way of the striae medullares to the trapezoid body and lateral lemniscus and the nuclei associated with the former, and partly transversely beneath the inferior peduncle and spinal tract of the trigeminal to the trapezoid body. Axons from the ventral cochlear nucleus pass partly by the striae medullares but for the most part horizontally to the trapezoid body.

The superior olivary nucleus is a small mass of gray matter situated on the dorsal surface of the lateral part of the trapezoid body. Some of its axons pass backward to the abducent nucleus, this bundle is known as the peduncle of the su-perior olivary nucleus. Other fibers from the nucleus join the posterior longitudinal bundle and terminate in the nuclei of the trochlear and oculomotor nerves. The majority of its axons, after giving off collaterals to the nucleus itself join the lat -eral lemniscus of the same side, other axons pass in the trapezoid body toward the ventral portion of the cochlear nucleus.

The nucleus of the trapezoid body lies between the root fibers of the abducent nerve and the superior olivary nu-cleus. Its cells lie among the fibers of the trapezoid body. In it terminate fibers and collaterals of the trapezoid body which come from the cochlear nucleus of the opposite and probably the same side and from the opposite trapezoid nucleus. They terminate in the nucleus of the trapezoid body in diffuse arborizations and peculiar end plaques or acoustic calyces of yel-lowish color which fuse with the cell bodies. Its cells are round and of medium size; their axons pass into the trapezoid body, cross the median line and probably join the lateral fillet.

The lateral preolivary or semilunar nucleus lies ventral to the superior olivary nucleus. In it end terminals and col-laterals of the trapezoid body and probably fibers of the opposite cochlear nucleus. Its axons mingle with the trapezoid body and join the lateral fillet.

The mesial preolivary nucleus is in contact with the ventral side of the nucleus of the trapezoid body. It receives many collaterals from the trapezoid body. Its cells are smaller than those of the trapezoid nucleus, their axons join the lat -eral fillet.

The lateral lemniscus (lateral fillet), the continuation upward of the central path of hearing, consists of fibers which come from the cochlear nuclei of the same and the opposite side by way of the trapezoid body and from the preolivary nu-clei. It lies in the ventral or ventro-lateral part of the reticular formation of the pons, at first ventral then lateral to the me -dian fillet. Above the pons these ascending fibers come to the surface at the side of the reticular formation in the trigonum

lemnisci and are covered by a layer of ependyma. This part of the lateral lemniscus is known as the fillet of Reil. On reach-ing the level of the inferior colliculus the dorsal fibers which overlie the superior peduncle decussate in the velum medullare anterius with similar fibers of the opposite side. Numerous small masses of cells are scattered along the path of the lateral lemniscus above the superior olivary nucleus and constitute lower and upper nuclei of the lateral lemniscus. They are supplied with many collaterals and possibly terminals from the fibers of the lemniscus. The axons of the lower nu-cleus of the lateral lemniscus, which arise from the larger stellate or spindle-shaped cells, with long, smooth, much branched dendrites, are said by some authors to join the lateral lemniscus, but according to Cajal they pass medially toward the raphé; their termination is unknown. The cells of the upper nucleus of the lateral lemniscus are more scattered. The same uncertainty exists in regard to their termination.

The fibers of the lateral lemniscus end by terminals or collaterals in the inferior colliculus and the medial geniculate body. A few of the fibers are said to pass by the inferior colliculus to terminate in the middle portion of the stratum griseum of the superior colliculus, and are probably concerned with reflex movements of the eyes depending on acoustic stimuli.

The inferior colliculi (lower or posterior quadrigeminal bodies) are important auditory reflex centers. Each consists of a compact nucleus of gray matter covered by a superficial white layer and separated from the central gray matter about the aqueduct by a thin, deep, white layer. Many of the axons which appear in the superficial white layer ascend through the inferior brachium to the medial geniculate body. Others mainly from large cells in the dorso-mesial part of the nucleus pass through the deep white layer into the tegmentum of the same and the opposite side and descend. Their termination is un-known, but they probably constitute an auditory reflex path to the lower motor centers, perhaps descending into the spinal cord with the tectospinal fasciculus. Other axons are said to descend in the lateral lemniscus to the various nuclei in the au -ditory path (Held) and probably to motor nuclei of the medulla and spinal cord.

The medial geniculate body receives terminals and collaterals from the lateral lemniscus (the central auditory path) and also large numbers of axons from the inferior colliculus of the same side and a few from the opposite side. It is thus a station in the central auditory path. A large proportion of its axons pass forward beneath the optic tract to join the corona radiata and then sweep backward and lateralward as the auditory radiation to terminate in the cortex of the superior tempo-ral gyrus. V. Monakow holds that Golgi cells type II are interpolated between the terminations of the incoming fibers to the medial geniculate body and the cells located there which give rise to the fibers of the auditory radiation. the medial genicu -late bodies are united by the long, slender commissure of Gudden. These fibers join the optic tract as it passes over the edge of the medial geniculate and passes through the posterior part of the optic chiasma. It is probably a commissure con-nected with the auditory system.

The Vestibular Nerve (vestibular root, VIII cranial) arise from the bipolar cells in the vestibular ganglion (Scarpa’s ganglion). The peripheral fibers end in the semicircular canals, the saccule and the utricle, the end-organs concerned with mechanism for the maintenance of bodily equilibrium. The central fibers enter the medulla oblongata and pass between the inferior peduncle and the spinal tract of the trigeminal. They bifurcate into ascending and descending branches as do the dorsal root fibers of all the spinal nerves and all afferent cranial nerves. The descending branches terminate in the dorsal (medial) vestibular nucleus, the principal nucleus of the vestibular nerve. This nucleus is prolonged downward into a de-scending portion in which end terminals and collaterals of the descending branch. The ascending branches pass to Deiters’s nucleus, to Bechterew’s nucleus and through the inferior peduncle of the cerebellum to the nucleus tecti of the opposite side.

The dorsal vestibular nucleus (medial or principal nucleus) is a large mass of small cells in the floor of the fourth ventricle under the area acustica, located partly in the medulla and partly in the pons. The striae medullares cross the upper part of it. It is separated from the median plane by the nucleus intercalatus. Its axons pass into the posterior longitudinal bundle of the same and the opposite side and ascend to terminate in the nucleus abducens of the same side and in the trochlear nucleus and the oculo-motor nucleus of the opposite side, and to the motor nuclei of the trigeminal on both sides. The descending portion, the nucleus of the descending tract extends downward as far as the upper end of the nucleus gra -cilis, and the decussation of the medial lemniscus. It is sometimes called the inferior vestibular nucleus. Many of its ax-ons cross the midline and probably ascend with the medial lemniscus to the ventro-lateral region of the thalamus.

The lateral vestibular nucleus (Deiters’s nucleus) is the continuation upward and lateralward of the principal nu-cleus, and in it terminate many of the ascending branches of the vestibular nerve. It consists of very large multipolar cells whose axons form an important part of the posterior longitudinal bundle of the same and the opposite side. The axons bifur-cate as they enter the posterior longitudinal bundle, the ascending branches send terminals and collaterals to the motor nu-clei of the abducens, trochlear and oculomotor nerves, and are concerned in coördinating the movements of the eyes with alterations in the position of the head; the descending branches pass down in the posterior longitudinal bundle into the ante-rior funiculus of the spinal cord as the vestibulospinal fasciculus (anterior marginal bundle) and are distributed to motor nu-clei of the anterior column by terminals and collaterals. Other fibers are said to pass directly to the vestibulospinal fascicu -lus without passing into the posterior longitudinal bundle. The fibers which pass into the vestibulospinal fasciculus are inti-mately concerned with equilibratory reflexes. Other axons from Deiters’s nucleus are supposed to cross and ascend in the opposite medial lemniscus to the ventro-lateral nuclei of the thalamus; still other fibers pass into the cerebellum with the in-ferior peduncle and are distributed to the cortex of the vermis and the roof nuclei of the cerebellum; according to Cajal they merely pass through the nucleus fastigii on their way to the cortex of the vermis and the hemisphere.

The superior vestibular nucleus (Bechterew’s nucleus) is the dorso-lateral part of the vestibular nucleus and re-ceives collaterals and terminals from the ascending branches of the vestibular nerve. Its axons terminate in much the same manner as do those from the lateral nucleus.

The Facial Nerve (VII cranial) consists of somatic sensory, sympathetic afferent, taste, somatic motor and sympa-thetic efferent fibers. The afferent or sensory fibers arise from cells in the geniculate ganglion. This portion of the nerve is often described as the nervus intermedius.

(1) The somatic sensory fibers are few in number and convey sensory impulses from the middle ear region. Their existence has not been fully confirmed. Their central termination is likewise uncertain, it is possible that they join the spinal tract of the trigeminal as do the somatic sensory fibers of the vagus and glossopharyngeal.

(2) The sympathetic afferent fibers are likewise few in number and of unknown termination. (3) Taste fibers convey impulses from the anterior two-thirds of the tongue via the chorda tympani. They are sup-

posed to join the tractus solitarius and terminate in its nucleus. The central connections of this nucleus have already been considered.

(4) Somatic motor fibers, supplying the muscles derived from the hyoid arch, arise from the large multipolar cells of the nucleus of the facial nerve. This nucleus is serially homologous with the nucleus ambiguus and lateral part of the an-terior column of the spinal cord. Voluntary impulses from the cerebral cortex are conveyed by terminals and collaterals of the pyramidal tract of the opposite side, indirectly, that is with the interpolation of a connecting neuron, to the facial nu -cleus. This nucleus undoubtedly receives many reflex fibers from various sources, i. e., from the superior colliculus via the ventral longitudinal bundle (tectospinal fasciculus) for optic reflexes; from the inferior colliculus via the auditory reflex path; and indirectly from the terminal sensory nuclei of the brain-stem. Through the posterior longitudinal bundle it is inti -mately connected with other motor nuclei of the brain-stem.

(5) Sympathetic efferent fibers (preganglionic fibers) arise according to some authors from the small cells of the facial nucleus, or according to others from a special nucleus of cells scattered in the reticular formation, dorso-medial to the facial nucleus. This is sometimes called the superior salivatory nucleus. These preganglionic fibers are distributed partly via the chorda tympani and lingual nerves to the submaxillary ganglion, thence by postganglionic (vasodilator) fibers to the submaxillary and sublingual glands. Some of the preganglionic fibers pass to the sphenopalatine ganglion via the great su -perficial petrosal nerve.

The Abducens Nerve (VI cranial) contains somatic motor fibers only which supply the lateral rectus muscle of the eye. The fibers arise from the nucleus of the abducens nerve and pass ventrally through the formatio reticularis of the pons to emerge in the transverse groove between the caudal edge of the pons and the pyramid. The nucleus is serially homolo-gous with the nuclei of the trochlear and oculomotor above and with the hypoglossal and medial part of the anterior column of the spinal cord below. It is situated close to the floor of the fourth ventricle, just above the level of the striae medullares. Voluntary impulses from the cerebral cortex are conducted by the pyramidal tract fibers (corticopontine fibers). These fibers probably terminate in relation with association neurons which control the coördinated action of all the eye muscles. This association and coördination mechanism is interposed between the terminals and collaterals of the voluntary fibers and the neurons within the nuclei of origin of the motor fibers to the eye muscles. The fibers of the posterior longitudinal bun-dle are supposed to play an important role in the coördination of the movements of the eyeball. Whether it is concerned only with coördinations between the vestibular apparatus and the eye or with more extensive coördinations is unknown. Many fibers of the posterior longitudinal bundle have their origin in the terminal nuclei of the vestibular nerve and from the posterior longitudinal bundle many collaterals and terminals are given off to the abducent nucleus as well as to the trochlear and oculomotor nuclei. The abducens nucleus probably receives collaterals and terminals from the ventral longitudinal bun-dle (tectospinal fasciculus); fibers which have their origin in the superior colliculus, the primary visual center, and are con-cerned with visual reflexes. Others probably come from the reflex auditory center in the inferior colliculus and from other sensory nuclei of the brain-stem.

The Trigeminal Nerve (V cranial) contains somatic motor and somatic sensory fibers. The motor fibers arise in the motor nucleus of the trigeminal and pass ventro-laterally through the pons to supply the muscles of mastication. The sen -sory fibers arise from the unipolar cells of the semilunar ganglion; the peripheral branches of the T-shaped fibers are dis-tributed to the face and anterior two-thirds of the head; the central fibers pass into the pons with the motor root and bifur-cate into ascending and descending branches which terminate in the sensory nuclei of the trigeminal.

The motor nucleus of the trigeminal is situated in the upper part of the pons beneath the lateral angle of the fourth ventricle. It is serially homologous with the facial nucleus and the nucleus ambiguus (motor nucleus of the vagus and glos -sopharyngeal) which belong to the motor nuclei of the lateral somatic group. The axons arise from large pigmented multi-polar cells. The motor nucleus receives reflex collaterals and terminals, (1) from the terminal nucleus of the trigeminal of the same and a few from the opposite side, via the central sensory tract (trigeminothalamic tract); (2) from the mesen-cephalic root of the trigeminal; (3) from the posterior longitudinal bundle; (4) and probably from fibers in the formatio reticularis. It also receives collaterals and terminals from the opposite pyramidal tract (corticopontine fibers) for voluntary movements. There is probably a connecting or association neuron interposed between these fibers and the motor neurons.

The terminal sensory nucleus consists of an enlarged upper end, the main sensory nucleus, and a long more slen-der descending portion which passes down through the pons and medulla to become continuous with the dorsal part of the posterior column of the gray matter especially the substantia gelatinosa of the spinal cord. This descending portion consists mainly of substantia gelatinosa and is called the nucleus of the spinal tract of the trigeminal nerve.

The main sensory nucleus lies lateral to the motor nucleus beneath the superior peduncle. It receives the short as-cending branches of the sensory root. The descending branches which form the tractus spinalis, pass down through the pons and medulla on the lateral side of the nucleus of the tractus spinalis, in which they end by collaterals and terminals, into the spinal cord on the level of the second cervical segment. It decreases rapidly in size as it descends. At first it is lo -cated between the emergent part of the facial nerve and the vestibular nerve, then between the nucleus of the facial nerve and the inferior peduncle. Lower down in the upper part of the medulla it lies beneath the inferior peduncle and is broken up into bundles by the olivocerebellar fibers and the roots of the ninth and tenth cranial nerves. Finally it comes to the sur -face of the medulla under the tubercle of Rolando and continues in this position lateral to the fasciculus cuneatus as far as the upper part of the cervical region where it disappears.

The cells of the sensory nucleus are of large and medium size and send their axons into the formatio reticularis where they form a distinct bundle, the central path of the trigeminal (trigeminothalamic tract), which passes upward through the formatio reticularis and tegmentum to the ventro-lateral part of the thalamus. Most of the fibers cross to the trigeminothalamic tract of the opposite side. This tract lies dorsal to the medial fillet; approaches close to it in the tegmen -tum and terminates in a distinct part of the thalamus. From the thalamus impulses are conveyed to the somatic sensory area of the cortex by axons of cells in the thalamus through the internal capsule and corona radiata. Many collaterals are given off in the medulla and pass from the trigeminothalamic tract to the motor nuclei, especially to the nucleus ambiguus, the fa -cial nucleus and the motor nucleus of the trigeminal.

The somatic sensory fibers of the vagus, the glossopharyngeal and the facial nerves probably end in the nucleus of the descending tract of the trigeminal and their cortical impulses are probably carried up in the central sensory path of the trigeminal.

The mesencephalic root (descending root of the trigeminal) arises from unipolar cells arranged in scattered groups in a column at the lateral edge of the central gray matter surrounding the upper end of the fourth ventricle and the cerebral aqueduct. They have usually been considered as motor fibers that join the motor root, but Johnston claims that they join the sensory root of the trigeminal, that they develop in the alar, not in the basal lamina, and that the pear-shaped unipolar cells are sensory in type.

The Trochlear Nerve (IV cranial) contains somatic motor fibers only. It supplies the superior oblique muscle of the eye. Its nucleus of origin, trochlear nucleus, is a small, oval mass situated in the ventral part of the central gray matter of the cerebral aqueduct at the level of the upper part of the inferior colliculus. The axons from the nucleus pass downward in the tegmentum toward the pons, but turn abruptly dorsalward before reaching it, and pass into the superior medullary velum, in which they cross horizontally, to decussate with the nerve of the opposite side, and emerges from the surface of the velum, immediately behind the inferior colliculus. The cells of the trochlear nucleus are large, irregular and yellowish in color. The nuclei of the two sides are separated by the raphé through which dendrites extend from one nucleus to the other. They receive many collaterals and terminals from the posterior longitudinal bundle which lies on the ventral side of the nucleus.

There are no branches from the fibers of the pyramidal tracts to these nuclei; the volitional pathway must be an indi-rect one, as is the case with other motor nuclei.

The Oculomotor Nerve (III cranial) contains somatic motor fibers to the Obliquus inferior, Rectus inferior, Rectus superior, Levator palpebrae superioris and Rectus medialis muscles and sympathetic efferent fibers (preganglionic fibers) to the ciliary ganglion. The postganglionic fibers connected with these supply the ciliary muscle and the sphincter of the iris. The axons arise from the nucleus of the oculomotor nerve and pass in bundles through the posterior longitudinal bun -dle, the tegmentum, the red nucleus and the medial margin of the substantia nigra in a series of curves and finally emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.

The oculomotor nucleus lies in the gray substance of the floor of the cerebral aqueduct subjacent to the superior colliculus and extends in front of the aqueduct a short distance into the floor of the third ventricle. The inferior end is con -tinuous with the trochlear nucleus. It is from 6 to 10 mm. in length. It is intimately related to the posterior longitudinal bun -dle which lies against its ventro-lateral aspect and many of its cells lie among the fibers of the posterior longitudinal bun-dle. The nucleus of the oculomotor nerve contains several distinct groups of cells which differ in size and appearance from each other and are supposed to send their axons each to a separate muscle. Much uncertainty still exists as to which group supplies which muscle. There are seven of these groups or nuclei on either side of the midline and one medial nucleus. The cells of the anterior nuclei are smaller and are supposed to give off the sympathetic efferent axons. The majority of fibers arise from the nucleus of the same side some, however, cross from the opposite side and are supposed to supply the Rectus medialis muscle. Since oculomotor and abducens nuclei are intimately connected by the posterior longitudinal bundle this decussation of fibers to the Medial rectus may facilitate the conjugate movements of the eyes in which the Medial and Lat -eral recti are especially involved.

Many collaterals and terminals are given off to the oculomotor nucleus from the posterior longitudinal bundle and thus connect it with the vestibular nucleus, the trochlear and abducens nuclei and probably with other cranial nuclei. Fibers from the visual reflex center in the superior colliculus pass to the nucleus. It is also connected with the cortex of the occipi -tal lobe of the cerebrum by fibers which pass through the optic radiation. The pathway for voluntary motor impulses is probably similar to that for the abducent nerve.

The Optic Nerve or Nerve of Sight (II cranial) consists chiefly of coarse fibers which arise from the ganglionic layer of the retina. They constitute the third neuron in the series composing the visual path and are supposed to convey only visual impressions. A number of fine fibers also pass in the optic nerve from the retina to the primary centers and are sup -posed to be concerned in the pupillary reflexes. There are in addition a few fibers which pass from the brain to the retina; they are supposed to control chemical changes in the retina and the movements of the pigment cells and cones. Each optic nerve has, according to Salzer, about 500,000 fibers.

In the optic chiasma the nerves from the medial half of each retina cross to enter the opposite optic tract, while the nerves from the lateral half of each retina pass into the optic tract of the same side. The crossed fibers tend to occupy the medial side of each optic nerve, but in the chiasma and in the optic tract they are more intermingled. The optic tract is at -tached to the tuber cinereum and lamina terminalis and also to the cerebral peduncle as it crosses obliquely over its under surface. These are not functional connections. A small band of fibers from the medial geniculate body joins the optic tract as the latter passes over it and crosses to the opposite tract and medial geniculate body in the posterior part of the chiasma. This is the commissure of Gudden and is probably connected with the auditory system.

Most of the fibers of the optic tract terminate in the lateral geniculate body, some pass through the superior brachium to the superior colliculus, and others either pass over or through the lateral geniculate body to the pulvinar of the

thalamus. These end-stations are often called the primary visual centers.The lateral geniculate body consists of medium-sized pigmented nerve cells arranged in several layers by the pene-

trating fibers of the optic tract. Their axons pass upward beneath the longer fibers of the optic tract, the taenia semicircu -laris, the caudate nucleus and the posterior horn of the lateral ventricle where they join the optic radiation of Gratiolet. They pass backward and medially to terminate in the visuo-sensory cortex in the immediate neighborhood of the calcarine fissure of the occipital lobe. This center is connected with the one in the opposite side by commissural fibers which course in the optic radiation and the splenium of the corpus callosum. Association fibers connect it with other regions of the cortex of the same side.

The region of the pulvinar in which optic tract fibers terminate resembles in structure the lateral geniculate body. Its axons also have a similar course though in a somewhat more dorsal plane.

The superior colliculus receives fibers from the optic tract through the superior brachium. Some enter by the super-ficial white layer (stratum zonale), others appear to dip down into the gray cap (stratum cinereum) while others probably decussate across the midline to the opposite colliculus. Other fibers from the superior brachium pass into the stratum op-ticum (upper gray-white layer). Some of these turn upward into the gray cap while others terminate among the cells of this layer. Since the superior colliculi appear to be the central organs concerned in the control of eye-muscle movements and eye-muscle reflexes we should expect to find them receiving fibers from other sensory paths. Many fibers pass to the supe-rior colliculus from the medial fillet as the latter passes through the tegmentum bringing the superior colliculus into relation with the sensory fibers of the spinal cord. Fibers from the central sensory path of the trigeminal probably pass with these. Part of the ventral spinocerebellar tract (Gowers) is said to pass up through the reticular formation of the pons and mid-brain toward the superior colliculus and the thalamus. The superior colliculus is intimately connected with the central audi-tory path (the lateral lemniscus), as part of its fibers pass the inferior colliculus and terminate in the superior colliculus. They are probably concerned with reflex movements of the eyes depending on auditory stimuli. The superior colliculus is said to receive fibers from the stria medullaris thalamis of the opposite side which pass through the commissura habenulae and turn back to the roof of the mid-brain, especially to the superior colliculus. By this path both the primary and cortical olfactory centers are brought into relation with the eye-muscle reflex apparatus.

The fibers which pass to the nuclei of the eye muscles arise from large cells in the stratum opticum and stratum lem -nisci and pass around the ventral aspect of the central gray matter where most of them cross the midline in the fountain de -cussation of Meynert, and then turn downward to form the ventral longitudinal bundle. This bundle runs down partly through the red nucleus, in the formatio reticularis, ventral to the posterior longitudinal bundle of the mid-brain, pons and medulla oblongata into the ventral funiculus of the spinal cord where it is known as the tectospinal fasciculus. Some of the fibers are said to pass down with the rubrospinal tract in the lateral funiculus. Some fibers do not decussate but pass down in the ventral longitudinal bundle of the same side on which they arise unless possibly they come from the opposite collicu -lus over the aqueduct. From the ventral longitudinal bundle collaterals are given off to the nuclei of the eye muscles, the oculomotor, the trochlear and the abducens. Many collaterals pass to the red nucleus, and are probably concerned with the reflexes of the rubrospinal tract. The fibers of the tectospinal tract end by collaterals and terminals either directly or indi -rectly among the motor cells in the anterior column of the spinal cord.

The superior colliculus receives fibers from the visual sensory area of the occipital cortex; they pass in the optic ra -diation. Probably no fibers pass from the superior colliculus to the visual sensory cortex.

The Olfactory Nerves (I cranial) or nerves of smell arise from spindle-shaped bipolar cells in the surface epithe-lium of the olfactory region of the nasal cavity. The non-medullated axons pass upward in groups through numerous foram-ina in the cribriform plate to the olfactory bulb; here several fibers, each ending in a tuft of terminal filaments, come into relation with the brush-like end of a single dendrite from a mitral cell. This interlacing gives rise to the olfactory glomeruli of the bulb. The termination of several or many olfactory fibers in a single glomerulus where they form synapses with the dendrites of one or two mitral cells provides for the summation of stimuli in the mitral cells and accounts in part at least for the detection by the olfactory organs of very dilute solutions. Lateral arborizations of the dendrites of the mitral cells and the connection of neighboring glomeruli by the axons of small cells of the glomeruli and the return of impulses of the mi-tral cells by collaterals either directly or through the interpolation of granule cells to the dendrites of the mitral cells rein -force the discharge of the mitral cells along their axons. The axons turn abruptly backward in the deep fiber layer of the bulb to form the olfactory tract. The olfactory tract is continued into the olfactory trigone, just in front of the anterior perfo -rated substance. The axons of the mitral cells on reaching the olfactory trigone separate into three bundles, the lateral ol-factory stria, the medial olfactory stria and the less marked intermedial olfactory stria.

The lateral olfactory striae curve lateralward, a few of the fibers end in the olfactory trigone and the antero-lateral portion of the anterior perforated substance. Most of the fibers, however, pass into the uncus, the anterior end of the hip -pocampal gyrus, and there end in the complicated cortex of the hippocampal gyri. The lateral striae more or less disappear as they cross the antero-lateral region of the anterior perforated substance.

The greater mass of the fibers of the olfactory tract pass into the lateral stria. Numerous collaterals are given into the plexiform layer of the subfrontal cortex, over which the striae pass on their way to the uncus, where they intermingle with the apical dendrons of the medium-sized and small pyramidal cells of the pyramidal layer of this subfrontal or frontal olfac-tory cortex. The axons give rise to projection fibers which take an antero-posterior direction to the subthalamic region send-ing collaterals and terminal branches to the stria medullaris and others toward the thalamus. Some of the fibers extend far -ther back and are believed to reach the pons and medulla oblongata.

Most of the fibers of the lateral olfactory stria pass to the hippocampal region of the cortex, especially to the gyrus hippocampi, which may be regarded as the main ending place of the secondary olfactory path derived from axons of the mitral cells.

The fibers of the medial olfactory striae terminate for the most part in the parolfactory area (Broca’s area), a few end in the subcallosal gyrus and a few in the anterior perforated substance and the adjoining part of the septum pellucidum. Some of the fibers pass into the anterior commissure (pars olfactoria) to the olfactory tract of the opposite side where they end partly within the granular layer and partly in the neighborhood of the glomeruli of the olfactory bulb, thus connecting the bulbs of the two sides.

The intermediate olfactory striae are as a rule scarcely visible, the fibers terminate in the anterior perforated sub-stance, a few are said to continue to the uncus.

The trigonum olfactorium, anterior perforated substance and the adjoining part of the septum pellucidum are impor-tant primary olfactory centers, especially for olfactory reflexes; in these centers terminate many axons from the mitral cells of the olfactory bulb. In addition the gray substance of the olfactory tract and the gyrus subcallosus receive terminals of the mitral cells.

The pathways from these centers to lower centers in the brain-stem and spinal cord are only partially known. The most direct path, the tractus olfactomesencephalicus (basal olfactory bundle of Wallenburg), is supposed to arise from cells in the gray substance of the olfactory tract, the olfactory trigone, the anterior perforated substance and the adjoining part of the septum pellucidum. The fibers are said to pass direct to the tuber cinereum, to the corpus mammillare, to the brainstem and the spinal cord. The fibers which enter the mammillary body probably come into relation with cells whose axons give rise to the fasciculus mammillo-tegmentalis (mammillo-tegmental bundle of Gudden) which is supposed to end in the gray substance of the tegmentum and of the aqueduct; some of its fibers are said to join the posterior longitudinal bundle and others to extend as far as the reticular formation of the pons.

Some of the fibers of the medial olfactory stria came into relation with cells in the parolfactory area of Broca and in the anterior perforated substance, whose axons course in the medullary stria of the thalamus. As the axons pass through the lower part of the septum pellucidum they are joined by other fibers whose cells receive impulses from the mitral cells. These fibers of the medullary stria end for the most part in the habenular nucleus of the same side, some, however, cross in the habenular commissure (dorsal part of the posterior commissure) to the habenular nucleus of the opposite side. A few fibers of the medullary stria are said to pass by the habenular nucleus to the roof of the mid-brain, especially the superior colliculus, while a few others come into relation with the posterior longitudinal bundle and association tracts of the mesen-cephalon.

The ganglion of the habenulae located in the trigonum habenulae just in front of the superior colliculus contains a mesial nucleus with small cells and a lateral nucleus with larger cells. The axons of these cells are grouped together in a bundle, the fasciculus retroflexus of Meynert, which passes ventrally medial to the red nucleus and terminates in a small medial ganglion in the substantia perforata posterior, immediately in front of the pons, called the interpeduncular gan-glion.

The interpeduncular ganglion has rather large nerve cells whose axons curve backward and downward as the tegmental bundle of Gudden, to end partly in the dorsal tegmental nucleus and surrounding gray substance where they come into relation with association neurons and the dorsal longitudinal bundle of Schütz.

The majority of the axons that arise from the mitral cells of the olfactory bulb and course in the olfactory tract course in the lateral olfactory stria to the uncus and hippocampal gyrus, and terminate in the cortex. Other fibers probably pass to the uncus and hippocampal gyrus from the primary olfactory centers in the trigonum and anterior perforated sub-stance. The gyrus hippocampus is continued through the isthmus into the gyrus cinguli which passes over the corpus callo-sum to the area parolfactoria. The cortical portions of these gyri are connected together by a thick association bundle, the cingulum, that lies buried in the depth of the gyrus cinguli extending forward to the parolfactory area and backward into the hippocampal region. The axons from the gyrus cinguli pass into the cingulum, many of them bifurcate, the anterior branches together with the axons which run in that direction are traceable as far forward as the anterior part of the septum pellucidum and the anterior end of the corpus striatum, where some of them are incorporated with projection fibers passing toward the internal capsule. The branches and axons which pass backward terminate partly in the hippocampus, the dentate gyrus and hippocampal gyrus. Shorter association fibers connect various sections of the gyrus fornicatus (cingulate gyrus, isthmus, and hippocampal gyrus) and these with other regions of the cortex. These gyri constitute the cortical center for smell.

The dentate gyrus which may be considered as a modified part of the hippocampus is partially separated from the gyrus hippocampus by the hippocampal fissure and from the fimbria by the fimbrio-dentate sulcus; it is intimately con-nected with the hippocampal gyrus and the hippocampus. When followed backward the dentate gyrus separates from the fimbria at the splenium, loses its incisions and knobs, and as the fasciola cinerea passes over the splenium onto the dorsal surface of the corpus callosum and spreads out into a thin layer of gray substance known as the indusium, which can be traced forward around the genu of the corpus callosum into the gyrus subcallosus. The white matter of the indusium known as the medial longitudinal striae (nerves of Lancisi) and the lateral longitudinal striae, are related to the indusium some-what as the cingulum is to the gyrus cinguli. Axons from the indusium pass into the longitudinal striae, some running for -ward and others backward while some after entering the medial longitudinal stria, pierce the corpus callosum to join the fornix. Some of the fibers which pass forward extend around the front of the corpus callosum and the anterior commissure, then curve downward, according to Cajal, to enter the corpus striatum where they join the olfactory projection-path. Other fibers are said to arise in the parolfactory area, the gyrus subcallosus and the anterior perforated substance (diagonal band of Broca) and course backward in the longitudinal striae to the dentate gyrus and the hippocampal region. The indu-sium is usually considered as a rudimentary part of the rhinencephalon.

The olfactory projection fibers which arise from the pyramid cells of the uncus and hippocampus and from the polymorphic cells of the dentate gyrus form a dense stratum on the ventricular surface, especially on the hippocampus, called the alveus. These fibers pass over into the fimbria and are continued into the fornix. About one-fourth of all the

fibers of the fimbria are large projection fibers, the other three-fourths consist of fine commissural fibers which pass from the hippocampus of one side through the fimbria and hippocampal commissure (ventral psalterium or lyre), to the fimbria and hippocampus of the opposite side where they penetrate the pyramidal layer and terminate in the stratum radiatum. The fibers which course in the fornix pass forward and downward into the corpora mammillare where numerous collaterals are given off and a few terminate. Most of the fibers in the fornix, however, pass through the corpora, cross the middle line and turn downward in the reticular formation in which they are said to be traceable as far as the pons and possibly farther. As the fornix passes beneath the corpus callosum it receives fibers from the longitudinal striae of the indusium and from the cingulum; these are the perforating fibers of the fornix which pass through the corpus callosum and course in the fornix to -ward the mammillary body. As the fornix passes the anterior end of the thalamus a few fibers are given off to the stria medullaris of the thalamus and turn back in the stria to the habenular ganglion of the same and the opposite side, having probably the same relation that the reflex fibers have which arise from the primary centers and course in the stria medullar -ies of the thalamus. Aside from the fibers of the fornix which pass through the mammillary body to decussate and descend (as the mammillo-mesencephalic fasciculus), many fibers are said to pass into the bundle of Vicq d’Azyr, and one bundle of fibers is said to pass from the fornix to the tuber cinereum.

The mammillary bodies receive collaterals and terminals then from the cortical centers via the fornix and probably other collaterals and terminals are received directly from the primary centers through the tractus olfactomesencephalicus. According to Cajal fibers also reach the mammillary body through the peduncle of the corpus mammillare from the arcuate fibers of the tegmentum and from the main fillet. The fornix probably brings the cortical centers into relation with the re-flex path that runs from the primary centers to the mammillary body and the tuber cinereum.

The bundle of Vicq d’Azyr (mammillo-thalamic fasciculus) arises from cells in both the medial and lateral nuclei of the mammillary body and by fibers that are directly continued from the fornix. There axons divide within the gray mat-ter; the coarser branches pass into the anterior nucleus of the thalamus as the bundle of Vicq d’Azyr, the finer branches pass downward as the mammillo-tegmental bundle of Gudden. The bundle of Vicq d’Azyr spreads out fan-like as it terminates in the anterior or dorsal nucleus of the thalamus. A few of the fibers pass through the dorsal nucleus to the angular nucleus of the thalamus. The axons from these nuclei are supposed to form part of the thalamocortical system.

The mammillo-tegmental bundle has already been considered under the olfactory reflex paths.The amygdaloid nucleus and the taenia semicircularis (stria terminalis) probably belong to the central olfactory

apparatus. The taenia semicircularis extends from the region of the anterior perforated substance to the nucleus amygdalae. Its anterior connections are not clearly understood. Fibers are said to arise from cells in the anterior perforated substance; some of the fibers pass in front of the anterior commissure, others join the fornix for a short distance as they pass behind the anterior commissure. The two strands ultimately join to form the taenia and pass backward in the groove between the caudate nucleus and the thalamus to the amygdaloid nucleus. Other fibers are said to pass in the opposite direction from the amygdaloid nucleus to the thalamus.

Practice skillsStudents are supposed to identify the following structures on the samples:

Self-taught class 9. Parasympathetic supplement of the head and neck.

The aim: to learn the parasympathetic supplement of head and heck.Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-

sents special interest for therapists, neurologists, neuropathologists and others.The plan of the self-taught class:

A. Revise the division of the parasympathetic nervous system into the cranial and pelvic parts.B. Learn the structures composing the cranial part of the parasympathetic nervous system.C. Learn the parasympathetic part of the oculomotor nerve – the accessory oculomotor nucleus – and the

course of fibers arising from it.D. Learn the composition and topography of the ciliary ganglion. Find out the organs innervated from the cil-

iary ganglion and the course of its fibers to these organs.E. Learn the parasympathetic part of the facial nerve – the superior salivatory nucleus – and the course of

fibers arising from it.F. Learn the composition and topography of the pterygopalatine, submandibular and sublingual ganglia. Find

out the organs innervated from these ganglia and the course of the fibers from the ganglia to these organs.G. Learn the parasympathetic part of the glossopharyngeal nerve – the inferior salivatory nucleus – and the

course of fibers arising from it.H. Learn the composition and topography of the otic ganglion. Find out the organ innervated from the otic gan-

glion and the course of its fibers to this organ.I. Learn the parasympathetic part of the vagus nerve – the dorsal nucleus – and the course of fibers arising

from it. Find out the organs of head and neck, innervated by the vagus nerve.

For more information see the practice classes 8 (Review of cranial nerves. I, II, ІІІ, ІV, VI, ХІ, ХІІ pairs of cranial nerves), 10 (The facial nerve (VIІ). The glossopharyngeal (ІХ) nerve), 11 (The vagus nerve (Х). The

parasympathetic nervous system) and self-taught class 8 (Review of the peripheral nervous system. Review of cranial nerves).

Self-taught class 10. Sympathetic supplement of the head and neck.

The aim: to learn the sympathetic supplement of head and heck.Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-

sents special interest for therapists, neurologists, neuropathologists and others.The plan of the self-taught class:

A. Revise the structure of the sympathetic nervous system, the localization of its centers and ganglia.B. Find out which sympathetic ganglia send fibers to the organs of head and neck.C. Learn the cervical portion of the sympathetic system.D. Learn the cephalic portion of the sympathetic system.

The Cervical Portion of the Sympathetic System(Pars Cervicalis S. Sympathici)The cervical portion of the sympathetic trunk consists of three ganglia, distinguished, according to their positions,

as the superior, middle, and inferior ganglia, connected by intervening cords. This portion receives no white rami com-municantes from the cervical spinal nerves; its spinal fibers are derived from the white rami of the upper thoracic nerves, and enter the corresponding thoracic ganglia of the sympathetic trunk, through which they ascend into the neck.

The superior cervical ganglion (ganglion cervicale superius), the largest of the three, is placed opposite the second and third cervical vertebrae. It is of a reddishgray color, and usually fusiform in shape; sometimes broad and flattened, and occasionally constricted at intervals; it is believed to be formed by the coalescence of four ganglia, corresponding to the up-per four cervical nerves. It is in relation, in front, with the sheath of the internal carotid artery and internal jugular vein; be-hind, with the Longus capitis muscle.

Its branches may be divided into inferior, lateral, medial, and anterior.The Inferior Branch communicates with the middle cervical ganglion.The Lateral Branches (external branches) consist of gray rami communicantes to the upper four cervical nerves

and to certain of the cranial nerves. Sometimes the branch to the fourth cervical nerve may come from the trunk connecting the upper and middle cervical ganglia. The branches to the cranial nerves consist of delicate filaments, which run to the ganglion nodosum of the vagus, and to the hypoglossal nerve. A filament, the jugular nerve, passes upward to the base of the skull, and divides to join the petrous ganglion of the glossopharyngeal, and the jugular ganglion of the vagus.

The Medial Branches (internal branches) are peripheral, and are the larnygopharyngeal branches and the supe-rior cardiac nerve.

The laryngopharyngeal branches (rami laryngopharyngei) pass to the side of the pharynx, where they join with branches from the glossopharyngeal, vagus, and external laryngeal nerves to form the pharyngeal plexus.

The superior cardiac nerve (n. cardiacus superior) arises by two or more branches from the superior cervical gan-glion, and occasionally receives a filament from the trunk between the first and second cervical ganglia. It runs down the neck behind the common carotid artery, and in front of the Longus colli muscle; and crosses in front of the inferior thyroid artery, and recurrent nerve. The course of the nerves on the two sides then differ. The right nerve, at the root of the neck, passes either in front of or behind the subclavian artery, and along the innominate artery to the back of the arch of the aorta, where it joins the deep part of the cardiac plexus. It is connected with other branches of the sympathetic; about the middle of the neck it receives filaments from the external laryngeal nerve; lower down, one or two twigs from the vagus; and as it enters the thorax it is joined by a filament from the recurrent nerve. Filaments from the nerve communicate with the thyroid branches from the middle cervical ganglion. The left nerve, in the thorax, runs in front of the left common carotid artery and across the left side of the arch of the aorta, to the superficial part of the cardiac plexus.

The Anterior Branches (nn. carotici externi) ramify upon the common carotid artery and upon the external carotid artery and its branches, forming around each a delicate plexus, on the nerves composing which small ganglia are occasion -ally found. The plexuses accompanying some of these arteries have important communications with other nerves. That sur-rounding the external maxillary artery communicates with the submaxillary ganglion by a filament; and that accompanying the middle meningeal artery sends an offset to the otic ganglion, and a second, the external petrosal nerve, to the genicu-lar ganglion of the facial nerve.

The middle cervical ganglion (ganglion cervicale medium) is the smallest of the three cervical ganglia, and is occa-sionally wanting. It is placed opposite the sixth cervical vertebra, usually in front of, or close to, the inferior thyroid artery. It is probably formed by the coalescence of two ganglia corresponding to the fifth and sixth cervical nerves.

It sends gray rami communicantes to the fifth and sixth cervical nerves, and gives off the middle cardiac nerve.The Middle Cardiac Nerve (n. cardiacus medius; great cardiac nerve), the largest of the three cardiac nerves,

arises from the middle cervical ganglion, or from the trunk between the middle and inferior ganglia. On the right side it de-scends behind the common carotid artery, and at the root of the neck runs either in front of or behind the subclavian artery; it then descends on the trachea, receives a few filaments from the recurrent nerve, and joins the right half of the deep part of the cardiac plexus. In the neck, it communicates with the superior cardiac and recurrent nerves. On the left side, the middle cardiac nerve enters the chest between the left carotid and subclavian arteries, and joins the left half of the deep part of the cardiac plexus.

The inferior cervical ganglion (ganglion cervicale inferius) is situated between the base of the transverse process of the last cervical vertebra and the neck of the first rib, on the medial side of the costocervical artery. Its form is irregular; it is larger in size than the preceding, and is frequently fused with the first thoracic ganglion. It is probably formed by the coalescence of two ganglia which correspond to the seventh and eighth cervical nerves. It is connected to the middle cervi -cal ganglion by two or more cords, one of which forms a loop around the subclavian artery and supplies offsets to it. This loop is named the ansa subclavia (Vieussenii).

The ganglion sends gray rami communicantes to the seventh and eighth cervical nerves.It gives off the inferior cardiac nerve, and offsets to bloodvessels.The inferior cardiac nerve (n. cardiacus inferior) arises from either the inferior cervical or the first thoracic gan-

glion. It descends behind the subclavian artery and along the front of the trachea, to join the deep part of the cardiac plexus. It communicates freely behind the subclavian artery with the recurrent nerve and the middle cardiac nerve.

The offsets to bloodvessels form plexuses on the subclavian artery and its branches. The plexus on the vertebral artery is continued on to the basilar, posterior cerebral, and cerebellar arteries. The plexus on the inferior thyroid artery ac -companies the artery to the thyroid gland, and communicates with the recurrent and external laryngeal nerves, with the su -perior cardiac nerve, and with the plexus on the common carotid artery.

The Cephalic Portion of the Sympathetic System (Pars Cephalica S. Sympathici)The cephalic portion of the sympathetic system begins as the internal carotid nerve, which appears to be a direct

prolongation of the superior cervical ganglion. It is soft in texture, and of a reddish color. It ascends by the side of the inter -nal carotid artery, and, entering the carotid canal in the temporal bone, divides into two branches, which lie one on the lat-eral and the other on the medial side of that vessel.

The lateral branch, the larger of the two, distributes filaments to the internal carotid artery, and forms the internal carotid plexus.

The medial branch also distributes filaments to the internal carotid artery, and, continuing onward, forms the cav-ernous plexus.

The internal carotid plexus (plexus caroticus internus; carotid plexus) is situated on the lateral side of the internal carotid artery, and in the plexus there occasionally exists a small gangliform swelling, the carotid ganglion, on the under surface of the artery. The internal carotid plexus communicates with the semilunar ganglion, the abducent nerve, and the sphenopalatine ganglion; it distributes filaments to the wall of the carotid artery, and also communicates with the tympanic branch of the glossopharyngeal nerve.

The communicating branches with the abducent nerve consist of one or two filaments which join that nerve as it lies upon the lateral side of the internal carotid artery. The communication with the sphenopalatine ganglion is effected by a branch, the deep petrosal, given off from the plexus on the lateral side of the artery; this branch passes through the carti -lage filling up the foramen lacerum, and joins the greater superficial petrosal to form the nerve of the pterygoid canal ( Vid-ian nerve), which passes through the pterygoid canal to the sphenopalatine ganglion. The communication with the tympanic branch of the glossopharyngeal nerve is effected by the caroticotympanic, which may consist of two or three delicate fila-ments.

The cavernous plexus (plexus cavernosus) is situated below and medial to that part of the internal carotid artery which is placed by the side of the sella turcica in the cavernous sinus, and is formed chiefly by the medial division of the internal carotid nerve. It communicates with the oculomotor, the trochlear, the ophthalmic and the abducent nerves, and with the ciliary ganglion, and distributes filaments to the wall of the internal carotid artery. The branch of communication with the oculomotor nerve joins that nerve at its point of division; the branch to the trochlear nerve joins it as it lies on the lateral wall of the cavernous sinus; other filaments are connected with the under surface of the ophthalmic nerve; and a sec -ond filament joins the abducent nerve.

The filaments of connection with the ciliary ganglion arise from the anterior part of the cavernous plexus and enter the orbit through the superior orbital fissure; they may join the nasociliary branch of the ophthalmic nerve, or be continued forward as a separate branch.

The terminal filaments from the internal carotid and cavernous plexuses are prolonged as plexuses around the ante-rior and middle cerebral arteries and the ophthalmic artery; along the former vessels, they may be traced to the pia mater; along the latter, into the orbit, where they accompany each of the branches of the vessel. The filaments prolonged on to the anterior communicating artery connect the sympathetic nerves of the right and left sides.

Written tests of cranial nervesI. Tests of basic theory1. Nerve fibers belonging to which cranial

nerve(s) are found in the pterygopalatine fossa?A. CN VB. CN VIIC. CN IXD. a and bE. *a, b and c

2. The mucosa covering most of the lingual tonsil would have sensory innervation by neurons whose cell bodies are in theA. geniculate ganglion B. *glossopharyngeal ganglionC. submandibular ganglionD. trigeminal ganglionE. vagal ganglion

3. Which of the following statements is/are TRUE? A. *the hypoglossal nerve passes lateral to the

internal and external carotid arteriesB. the hypoglossal nerve passes superior, lat-

eral, inferior and medial to the submandibu-lar duct

C. sensory innervation to the tongue travels in the hypoglossal nerve

D. a and b E. a and c

4. The gag reflex involves pharyngeal stimulation followed by contraction of the pharyngeal con-strictors. A successful reflex requires function-ingA. glossopharyngeal nervesB. vagus nervesC. *bothD. neither

5. Touching the upper eyelid or the corneal caused a blink reflex, but touching the lower eyelid did not. The problem is non-function of theA. entire ophthalmic nerveB. entire trigeminal nerveC. frontal nerve D. *infraorbital nerveE. nasociliary nerve

6. The temporomandibular joint syndrome is char-acterized by pain from the joint. The cell bodies of the pain fibers are in the:A. geniculate ganglionB. glossopharyngeal ganglionC. vagus ganglionD. otic ganglionE. *trigeminal ganglion

7. The facial nerve:A. *exits the skull through the stylomastoid

foramenB. divides into three major trunks in the

parotid glandC. supplies the parotid gland with parasympa-

thetic fibers

D. a and bE. None of the above are true concerning the

facial nerve8. Pain from swelling of the parotid gland, as in a

case of mumps, is transmitted towards the cen-tral nervous system in which nerve?A. lesser occipitalB. ascending branch of transverse cervical C. descending branch of transverse cervical D. temporal branch of facialE. *auriculotemporal

9. All the following are true for the trigeminal nerve EXCEPT:A. *it supplies motor innervation to the bucci-

nator muscleB. it supplies general sense to the conjunctiva

in the orbitC. it supplies general sense to the mucosa of

the mouthD. it supplies general sense to the nasal mu-

cosaE. it supplies general sense to the skin of the

face 10. During surgery of the right neck the accessory

nerve was cut. The ends were brought together and sutured. The surgery was completed. What signs and symptoms would be expected to be observed following the surgery but prior to re-generation of the nerve?A. difficulty in elevating the right shoulderB. difficulty in abduction of the right armC. difficulty in turning the head to the leftD. a and cE. *a, b, and c

11. To reach the intrinsic muscles of the larynx, their major nerve pierces theA. conus elasticusB. cricotracheal membraneC. *quadrangular membraneD. thyrohyoid membraneE. none of the above

12. Cell bodies of preganglionic fibers in the ptery-goid canal are located in theA. geniculate ganglionB. pterygopalatine ganglionC. superior cervical ganglionD. *superior salivatory nucleusE. c and d

13. An infection in the sublingual gland spreads to form an abscess around the gland beside the tongue. The nerve/s exposed to the abscess would be the:A. GlossopharyngealB. HypoglossalC. LingualD. *b and cE. a, b and c

14. The pharyngeal plexus innervates all of the fol-lowing EXCEPT:A. pharyngeal constrictorsB. *stylopharyngeus muscleC. palatopharyngeus muscleD. salpingopharyngeus muscleE. palatoglossus muscle

15. The nasociliary nerve:A. is a branch of the maxillary nerveB. *is made up of sensory fibersC. gives rise to the supratrochlear and supraor-

bital nerves D. its branches remain in the orbitE. all of the above

16. An acoustic neuroma (a space occupying tu-mor) in the internal acoustic meatus can pro-duce all of the following symptoms EXCEPT: A. decrease in salivationB. *increased lacrimationC. loss of hearingD. loss of taste to the anterior two-thirds of the

tongueE. paralysis of the buccinator muscle

17. The chorda tympani nerve:A. is a branch of the facial nerveB. traverses through the middle earC. contains parasympathetic and somatic mo-

tor fibersD. *a and bE. b and c

18. A patient had his mouth opened too wide while having a breathing tube inserted, causing the posterior part of the temporomandibular joint capsule to be tom. When he awakes, he will be conscious of pain impulses traveling in the:A. *auriculotemporal nerveB. buccal nerveC. inferior alveolar nerveD. nerve to the masseter muscleE. nerve to the medial pterygoid muscle

19. A deep vertical slash on the face extending from the zygomatic arch to the mid point of the inferior border of the mandible could result in:A. loss of ability to close the ipsilateral eyeB. a severed parotid ductC. loss of taste over the anterior two-thirds of

the tongueD. *a and bE. a, b, and c

20. A hard slap to the eye causes a "blow out" frac-ture of the floor of the orbit If the nerve travel-ing in the floor is severed, there will be sensory loss to all the following EXCEPT:A. ala of the noseB. lower eyelidC. *tip of the noseD. upper lipE. all of the above

21. The recurrent (or inferior) laryngeal nerve in-nervates all the intrinsic laryngeal muscles, EX-CEPT: A. lateral cricoarytenoid B. posterior cricoarytenoid C. cricothyroid D. vocalis E. aryepiglottis

22. The submandibular ganglion contains pregan-glionic parasympathetic axons from cranial nerve: A. III B. V C. VII D. IX E. X

23. A lesion of the facial nerve at its exit from the skull would result in: A. an ipsilateral loss of taste to the anterior

tongue B. a decrease in saliva delivered directly onto

the floor of the mouth C. a sensory loss to the tongue D. all of the above E. none of the above

24. The oculomotor nerve supplies motor innerva-tion to all the following muscles, EXCEPT: A. levator palpebrae superioris B. orbicularis oculi C. superior rectus D. medial rectus E. inferior oblique

25. The parasympathetic nervous system has origin in all the following cranial nerves, EXCEPT: A. oculumotor B. facial C. glossopharyngeal D. vagus E. trigeminal

26. The following statements concerning the facial nerve or its named branches are true, EXCEPT: A. The ganglion of the facial nerve is the

geniculate ganglion. B. The buccinator muscle is innervated by a

branch of the facial nerve. C. The greater petrosal N. is joined by a post-

ganglionic sympathetic nerve. D. Salivary glands are innervated by parasym-

pathetic fibers of the facial nerve.E. The anterior and posterior bellies of the di-

gastric are innervated by branches of the fa-cial nerve.

27. The motor division of the trigeminal nerve leaves the skull through the: A. Foramen rotundum B. Foramen ovale C. Superior orbital fissure D. Inferior orbital fissure E. Foramen spinosum

28. Pick the discordant pair: A. optic canal : optic nerve B. foramen ovale: mandibular division of the

trigeminal nerve C. jugular foramen : glossopharyngeal nerve D. superior orbital fissure : oculomotor n. E. internal acoustic meatus : abducens n.

29. The right recurrent laryngeal nerve usually loops around which of the following structures: A. aortic arch B. axillary A C. ligamentum arteriosum D. subclavian A E. ansa cervicalis

30. The nerve of the pterygoid canal contains: A. preganglionic parasympathetic fibers from

CNVII. B. postganglionic parasympathetic fibers from

CNVII. C. special sensory fibers from CNVII D. preganglionic sympathetic fibers E. none of the above

31. "Branches of the CNV include all of the follow-ing, EXCEPT:" A. lesser petrosal B. zygomatic C. frontal D. ethmoidal E. lacrimal

"Each group of questions below consists of lettered headings followed by a list of numbered word or phrase, select the one heading that is most closely related to it. A particular answer may be used once, more than once or not at all."

(a) stylomastoid foramen(b) jugular foramen(c) superior orbital fissure(d) carotid canal(e) foramen rotundum

32. a b c d e --maxillary nerve 33. a b c d e --trochlear nerve 34. a b c d e --postganglionic sympathetics 35. a b c d e --facial nerve 36. a b c d e --glossopharyngeal nerve 37.Matching Type

(a) cranial nerve II(b) cranial nerve V(c) cranial nerve VI(d) cranial nerve VII(e) cranial nerve XI

38. a b c d e --longest cranial nerve running in bone 39. a b c d e --has extra-cranial components 40. a b c d e --largest nerve seen in the skull 41. a b c d e --special sensory only 42. a b c d e --most sensitive to increased intracra-

nial pressure

43. Which of the following is a branch of the max-illary division of the trigeminal nerve? A. nasociliary N. B. mental N. C. lacrimal N. D. infraorbital N. E. chorda tympana N.

44. Ptosis of the eyelid may be caused by injury to the: A. nerve to the levator palpebrae superioris M. B. abducens N. C. superior oblique M. D. superior rectus M. E. facial N.

II. Tests from “Step-1” database (with explana-tion)1. A physician is performing a cranial nerve ex-

amination on a patient. While testing the gag re-flex, it is noted that when the right side of the pharyngeal mucosa is touched, the patient's uvula deviates to the right. When the left side of the pharyngeal mucosa is touched, the patient does not gag. Which of the following is the most likely location of his lesion?A. Left glossopharyngeal nerve and left vagus

nerveB. Left glossopharyngeal nerve onlyC. Left vagus nerve onlyD. Right glossopharyngeal nerve and right va-

gus nerveE. Right glossopharyngeal nerve onlyF. Right vagus nerve only

Explanation:The correct answer is A. The gag reflex requires the glossopharyngeal nerve for the sensory limb of the reflex (unilateral) and the vagus nerve for the motor limb of the reflex (bilateral). A lesion of the left glossopharyngeal nerve will denervate the sensory receptors on the left side of the pharynx. Thus when the left side is touched, the patient does not feel it and does not gag. The gag reflex requires the vagus nerve for the motor limb of the reflex. If the left va-gus nerve is lesioned, the left side of the soft palate will not elevate during a gag and the uvula will de-viate to the right. In this case, the patient only feels the touch on the right side and only elevates the right side of the palate. Thus there is a lesion of both the left glossopharyngeal nerve and the left va-gus nerve.If the patient had a lesion of the left glossopharyn-geal nerve only (choice B), there would have been no gag when the left side is touched but there would be a normal gag, without deviation of the uvula, when the right side was touched.If the patient had a lesion of the left vagus nerve only (choice C), the patient would have deviation of the uvula to the right when a gag was elicited, but touching either side of the pharynx would elicit a gag.

If the patient had a lesion of the right glossopharyn-geal nerve and the right vagus nerve (choice D), touching the right side of the pharynx would not elicit a gag and touching the left side of the pharynx would elicit a gag with the uvula deviating to the left.If the patient had a lesion of the right glossopharyn-geal nerve only (choice E), there would be no gag when the right side is touched but there would be a normal gag, without deviation of the uvula, when the left side was touched.If the patient had a lesion of the right vagus nerve only (choice F), the patient would have deviation of the uvula to the left when a gag was elicited and touching either side of the pharynx would elicit a gag.2. A patient's left hypoglossal nerve (CN XII) is

injured during a carotid endarterectomy. Which of the following would most likely result from this injury?A. Decreased gag reflex on the leftB. Decreased salivation from the left sub-

mandibular and sublingual salivary glandsC. Deviation of the tongue to the left on pro-

trusionD. Inability to elevate the pharynx on the left

during swallowingE. Inability to perceive sweet and salt taste

sensation on the anterior part of the left side of the tongue

Explanation:The correct answer is C. The hypoglossal nerve is a pure motor nerve (general somatic efferent) to the intrinsic muscles of the tongue. If the nerve is dam-aged, denervation atrophy of the affected side will permit the intact musculature of the opposite side to operate unopposed, thereby protruding the tongue to the side of the injury.The gag reflex (choice A) is mediated by the glos-sopharyngeal nerve (CN IX; afferent limb) and the vagus nerve (CN X; efferent limb).Choice B is incorrect because the preganglionic parasympathetic fibers that regulate these two sali-vary glands are carried by the chorda tympani (which joins with the lingual nerve) to the sub-mandibular ganglion. Postganglionic fibers are then distributed to these glands. The muscles responsible for elevation of the phar-ynx (choice D) are innervated primarily by the va-gus nerve (CN X).Choice E is incorrect because taste fibers for the an-terior two-thirds of the tongue are carried via the chorda tympani to the facial nerve (CN VII) and hence to the brainstem.

3. A patient develops an excruciatingly painful in-fection of the anterior half of the external ear canal. Which of the following nerves transmits this impulse?

A. Auricular branch of the vagusB. Auriculotemporal nerveC. Greater auricular nerveD. Lesser occipital nerveE. Vestibulocochlear nerve

Explanation:The correct answer is B. The ear has a complex sen-sory nerve supply, which includes all of the nerves listed. A consequence of this complexity is that pain actually originating in other sites (teeth and sinuses are notorious) may be misinterpreted as ear pain or (less commonly) pain originating in the ear may be misinterpreted as arising from other sites. The ante-rior half of the external ear canal is supplied by the auriculotemporal nerve, which also supplies the fa-cial surface of the upper part of the auricle.The auricular branch of the vagus (choice A) sup-plies the posterior half of the external ear canal.The greater auricular nerve (choice C) supplies both surfaces of the lower part of the auricle.The lesser occipital nerve (choice D) supplies the cranial surface of the upper part of the auricle.The vestibulocochlear nerve (choice E) supplies hearing and motion sense.4. A 55-year-old male mechanic suffers a stroke

while trying to replace a flat tire on the road. He has a history of hypertension, but had not been taking his medications regularly. In addition, he is a heavy smoker, and drinks a six-pack of beer every weekend. On examination, he is con-scious and has difficulty speaking clearly. A right upper motor neuron paralysis of the facial nerve is noted; the other cranial nerves are nor-mal. He has a dense hemiplegia on the right side, with equal paralysis of the arm and leg. His lesion most likely involves the A. convexity of the left frontal lobeB. convexity of the right frontal lobeC. corticospinal tract in the upper cervical

spinal cordD. left internal capsuleE. right internal capsule

Explanation:The correct answer is D. This patient has sustained a hemorrhage of the left internal capsule secondary to uncontrolled hypertension. The internal capsule receives its blood supply from the lenticulostriate arteries, which are prone to rupture in uncontrolled hypertension. The anterior limb of the internal cap-sule conveys frontopontine fibers, the genu con-ducts corticobulbar fibers, and the posterior limb of the internal capsule conveys corticospinal fibers to the contralateral arm and leg. Hemorrhage of the left internal capsule results in right-sided dense hemiplegia in which paralysis of the arm and leg are of the same intensity.The convexity of the frontal lobe (choices A and B) does not control the leg. This is done by the medial aspect of the cerebral hemisphere. Also, a hemor-

rhage involving the right frontal lobe (choice B) would affect the left side of the body. This patient has right-sided paralysis.Lesions of the corticospinal tract in the upper cervi-cal spinal cord (choice C) would result in hemi- or quadriparesis/plegia. The cranial nerves would not be involved.Hemorrhage involving the right internal capsule (choice E) would result in left-sided paralysis.5. A 22-year-old woman presents to her physician

with amenorrhea, weight loss, anxiety, tremor, heat intolerance and palpitations. Laboratory examination is consistent with hyperthyroidism, and the physician prescribes propylthiouracil. The patient's response to propylthiouracil is dis-appointing, and the symptoms recur, then worsen. Subtotal thyroidectomy is successfully performed, but following the surgery, the woman is extremely hoarse, and can barely speak above a whisper. This hoarseness is most probably related to damage to a branch which of the following cranial nerves?A. FacialB. GlossopharyngealC. HypoglossalD. TrigeminalE. Vagus

Explanation:The correct answer is E. The recurrent laryngeal nerves are branches of the vagus (CN X), and sup-ply all intrinsic muscles of the larynx except the cricothyroid. The right recurrent laryngeal nerve re-curs around the right subclavian artery. The left re-current laryngeal nerve recurs in the thorax around the arch of the aorta and ligamentum arteriosum. Both nerves ascend to the larynx by passing be-tween the trachea and esophagus, in close proximity to the thyroid gland. The recurrent laryngeal nerves are therefore particularly vulnerable during thyroid surgery, and damage may cause extreme hoarse-ness.The facial nerve (choice A) innervates the muscles of facial expression, the stapedius muscle, and the lacrimal, submandibular and sublingual glands. It also mediates taste sensation from the anterior two-thirds of the tongue.The glossopharyngeal nerve (choice B) innervates the stylopharyngeus muscle and the parotid gland. Visceral afferents supply the carotid sinus barore-ceptors and carotid body chemoreceptors, and me-diate taste from the posterior one-third of the tongue. Somatosensory fibers supply pain, tempera-ture, and touch information from the posterior one-third of the tongue, upper pharynx, middle ear, and eustachian tube.The hypoglossal nerve (choice C) innervates the in-trinsic muscles of the tongue, the genioglossus, hy-poglossus, and styloglossus muscles.

The trigeminal nerve (choice D) receives sensory information from the face and also innervates the muscles of mastication.6. A 12-year-old is seen by a pediatrician for a se-

vere sore throat. Physical examination reveals a brightly erythematous patch in the upper poste-rior pharynx. Which of the following cranial nerves would most likely carry the pain sensa-tion associated with this lesion?A. IIIB. VC. VIID. IXE. X

Explanation:The correct answer is D. The glossopharyngeal nerve (IX) carries general somatic sensation from the posterior part of the upper pharynx, eustachian tube, and posterior one-third of the tongue. It also carries taste sensation from the posterior one-third of the tongue, and conveys afferent fibers from the carotid sinus baroreceptors and carotid body chemoreceptors, and efferent fibers to the stylopha-ryngeus muscle.The oculomotor nerve (III, choice A) supplies the extraocular muscles (superior, inferior, and medial recti, and inferior oblique) and levator palpebrae su-perioris muscle, and sends parasympathetic fibers to the ciliary muscle and iris.The trigeminal nerve (V, choice B) receives somatic sensation information from the face, lips, gums, teeth, palate, and anterior two-thirds of the tongue.The facial nerve (VII, choice C) carries taste sensa-tion from the anterior two-thirds of the tongue. It supplies motor innervation to the muscles of facial expression and to the stapedius muscle, and sends parasympathetic fibers to the lacrimal, submandibu-lar, and sublingual glands.The vagus nerve (X, choice E) carries sensation from the lower part of the posterior pharynx, lar-ynx, trachea, and esophagus. It supplies parasympa-thetic innervation to the thoracic and abdominal vis-cera to the left colic flexure.7. As part of a complete neurological examination,

a medical student takes a cotton-tipped applica-tor and touches the patient's left eye with a thin wisp of cotton as the patient looks to the right. The patient closes both of his eyelids in re-sponse. Which of the following cranial nerves is responsible for the motor limb of this reflex?A. AbducensB. FacialC. OpticD. TrigeminalE. Trochlear

Explanation:The correct answer is B. The corneal reflex is tested by touching the cornea of one eye with a cotton wisp; this causes both eyes to close. The afferent, or

sensory, component of the corneal reflex is medi-ated by the ophthalmic division of the ipsilateral trigeminal nerve (V-1). The efferent, or motor, component is mediated by the facial nerve (CN VII), bilaterally.The abducens nerve (CN VI; choice A) innervates the lateral rectus muscles, which abduct the eyes.The optic nerve (CN II; choice C) is responsible for vision, providing the afferent limb of the pupillary light reflex.The trigeminal nerve (CN V; choice D) is responsi-ble for the afferent limb of the corneal reflex. It also innervates the muscles of mastication and provides sensory innervation to the face.The trochlear nerve (CN IV; choice E) innervates the superior oblique muscles, which depress, intort, and abduct the eyes.III. Tests from “Krok-1” database1. A 54-year-old man was admitted to a neuro-

surgery department with complaints of skin sensitivity absence of the inferior eyelid, lateral surface of the nose, upper lip. During examina-tion the doctor determined the inflammation of the second branch of the trigeminal nerve. Through what cranial foramen does this branch come out?A. Spinal.B. Lacerated.C. Oval.D. *Round.E. Superior orbital fissure.

2. A man of 45 appealed to a clinic complaining of sensitivity loss in the back third of the tongue. The function of which pair of crainal nerves was affected?A. VIII.B. X.C. *IXD. VE. XII.

3. Which nerve is damaged, if the right nasolabial fold is smoothed, right orbital fissure is dilated (it cannot be screwed up because eyelids don't close), difficulties arouse while talking and eat-ing (food sticks between the cheek and teeth)?A. N. trigeminus dexter.B. N. abducens dexter.C. N. glossopharyngeus sinister.D. N. vagus dexter.E. *N. facialis dexter.

4. After a cranial trauma with the damage of the superior wall of the right eyesocket a patient lost the possibility to lift up the upper eyelid of the right eye and look up. Which nerve was damaged?A. N. ophtalmicus.B. R. inferior n. oculomotorius.C. N. trochlearis.D. N. abducens.

E. *R. superior n. oculomotorius.5. A patient with aneurism of the right subclavian

artery has a husky voice. Irritation of which nerve can it be connected with?A. N. laryngeus superior dexter.B. *N. laryngeus recurrens dexter.C. N. laryngeus recurrens sinister.D. N. laryngeus superior sinister.E. N. laryngeus inferior sinister.

6. A patient was admitted to a neurological depart-ment with deflection of the tongue to the side when extruded, atrophic changes of the half of the tongue, logopathy, deglutitive problem. Which nerve was damaged?A. Vagus.B. Lingual.C. Chorda tympani.D. Glossopharyngeal.E. *Hypoglossal.

7. A patient can not lift an eyebrow on one half of his face, close eyelids, and bare his teeth. Which nerve is injured?A. Maxillary.B. Ophthalmic.C. *Facial.D. Mandibular.E. Oculomotor.

8. A 60-year-old patient has difficulties forming and moving a bolus. The tongue is immovable, logopathy is observed. Which nerve has been injured?A. *Sublingual.B. Accessory.C. Glossopharyngeal.D. Trigeminal.E. Facial.

9. After a cold a patient had incomplete eyeball abduction. Which nerve was injured?A. Facial.B. Glossopharyngeal.C. Trochlear.D. Optic.E. *Abducent.

10. A patient has a tongue motor function disorder. Which nerve was injured?A. Accessory.B. Vagus.C. Glossopharyngeal.D. Facial.E. *Hypoglossal.

11. After a cold a patient had disorder of pain and temperature sensitivity of anterior 2/3 of the tongue. Which nerve was injured?A. Sublingual.B. *Trigeminal.C. Phrenic.D. Vagus.E. Chorda tympani.

12. After a cold a patient has a feeling of facial numbness on the right. Examination has shown disorders of pain and temperature sensitivity of the right half of the face. Which nerve has been injured?A. Sublingual.B. Facial.C. Glossopharyngeal.D. Vagus.E. *Trigeminal.

13. A patient with epidemic encephalitis has uni- or bilateral ptosis (blepharoptosis), divergent stra-bismus, accommodation disorder, mydriatic pupils. The nuclei of what pair of cranial nerves have been affected?A. *III.B. IV.C. V.D. VI.E. VII.

14. As a result of a pathological process the func-tion of the efferent part central link of the vege-tative nervous system sympathetic department was affected. Point out possible localization of the process in the spinal cord.A. *Lateral intermediate nucleus of lateral

horns.B. Medial intermediate nucleus of lateral

horns.C. Dorsal nucleus of posterior horns.D. Proper nucleus of posterior horns.E. Central nucleus of anterior horns.

15. After an oral cavity soft tissues injure a patient lost gustation of the posterior third of the tongue. What nerve was injured?A. *Glossopharyngeal.B. Facial.C. Hypoglossal.D. Lingual.E. Chorda tympani.

16. A head trauma caused a hematoma in the zone of the middle cranial fossa on the left which led to a mydriatic pupil on the affected side. What nerve was injured?A. Trigeminal.B. Abducent.C. Ophthalmic.D. Trochlear.E. *Oculomotor.

17. During the initial examination a patient does not have general sensitivity of the anterior 2/3 of the tongue. Gustation is preserved. What nerve was injured?A. *Lingual branch of trigeminal nerve up to

its conjugation with chorda tympani.B. Sublingual nerve.C. Lingual branch of trigeminal nerve after its

conjugation with chorda tympani.D. Chorda tympani of facial nerve.E. Glossopharyngeal nerve.

18. A patient has lacrimation and increased saliva-tion. In combination with other symptoms this state is considered to be an irritation of fibers of a cranial nerve. Which nerve is this, and what fibers are these?A. *Parasympathetic fibres of facial nerve.B. Parasympathetic fibres of oculomotor

nerve.C. Somatic motor fibres of oculomotor nerve.D. Parasympathetic fibres of vagus nerve.E. Somatic motor fibres of facial nerve.

19. Examination of pupillary reflex has shown as-thenocoria. Which nucleus function is dam-aged?A. *Accessory nucleus of oculomotor nerve.B. Nucleus of trochlear nerve.C. Nucleus of abducent nerve.D. Nucleus of superior tubercles of tectum of

mesencephalon.E. Nucleus of oculomotor nerve.

UNIT 14. THE VESSELS OF HEAD AND NECKPractice class 12. Written tests and examination of practice skills of cranial nerves. Exami-

nation of self-taught tasks. The arch of aorta. The common carotid and subclavian arteries.

The aim: to learn the characteristic of the arch of aorta; to learn the topography, branches and area of blood supply of the subclavian and common carotid artery .

Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-sents special interest for therapists.

The plan of the practice class:A. Checking of the home assignment: oral quiz or written test control – 30 minutes.B. Summary lecture on the topic by teacher – 30 minutes.

a) The arch of aorta, its topography, peculiarities and branches.b) The subclavian artery, its topography, peculiarities and branches.c) The common carotid artery, its topography, peculiarities and branches.

C. Students’ self-taught time – 55 minutesD. Home-task – 5 minutes

The Arch of the Aorta (Arcus Aortae; Transverse Aorta).—The arch of the aorta begins at the level of the up-per border of the second sternocostal articulation of the right side, and runs at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left side of the trachea and finally passes downward on the left side of the body of the fourth thoracic vertebra, at the lower border of which it becomes continuous with the descending aorta. It thus forms two curvatures: one with its convexity upward, the other with its convexity forward and to the left. Its upper border is usually about 2.5 cm. below the superior border to the manubrium sterni.

Relations.—The arch of the aorta is covered anteriorly by the pleurae and anterior margins of the lungs, and by the remains of the thymus. As the vessel runs backward its left side is in contact with the left lung and pleura. Passing down-ward on the left side of this part of the arch are four nerves; in order from before backward these are, the left phrenic, the lower of the superior cardiac branches of the left vagus, the superior cardiac branch of the left sympathetic, and the trunk of the left vagus. As the last nerve crosses the arch it gives off its recurrent branch, which hooks around below the vessel and then passes upward on its right side. The highest left intercostal vein runs obliquely upward and forward on the left side of the arch, between the phrenic and vagus nerves. On the right are the deep part of the cardiac plexus, the left recurrent nerve, the esophagus, and the thoracic duct; the trachea lies behind and to the right of the vessel. Above are the innominate, left common carotid, and left subclavian arteries, which arise from the convexity of the arch and are crossed close to their ori -gins by the left innominate vein. Below are the bifurcation of the pulmonary artery, the left bronchus, the ligamentum arte-riosum, the superficial part of the cardiac plexus, and the left recurrent nerve. As already stated, the ligamentum arteriosum connects the commencement of the left pulmonary artery to the aortic arch.

Between the origin of the left subclavian artery and the attachment of the ductus arteriosus the lumen of the fetal aorta is considerably narrowed, forming what is termed the aortic isthmus, while immediately beyond the ductus arteriosus the vessel presents a fusiform dilation which His has named the aortic spindle—the point of junction of the two parts being marked in the concavity of the arch by an indentation or angle. These conditions persist, to some extent, in the adult, where His found that the average diameter of the spindle exceeded that of the isthmus by 3 mm.

Distinct from this diffuse and moderate stenosis at the isthmus is the condition known as coarctation of the aorta, or marked stenosis often amounting to complete obliteration of its lumen, seen in adults and occuring at or near, oftenest a lit -tle below, the insertion of the ligamentum arteriosum into the aorta. According to Bonnet 96 this coarctation is never found in the fetus or at birth, and is due to an abnormal extension of the peculiar tissue of the ductus into the aortic wall, which gives rise to a simultaneous stenosis of both vessels as it contracts after birth—the ductus is usually obliterated in these cases. An extensive collateral circulation is set up, by the costocervicals, internal mammaries, and the descending branches of the transverse cervical above the stenosis, and below it by the first four aortic intercostals, the pericardiaco-phrenics, and the superior and inferior epigastrics.

Peculiarities.—The height to which the aorta rises in the thorax is usually about 2.5 cm. below the upper border of the sternum; but it may ascend nearly to the top of the bone. Occasionally it is found 4 cm., more rarely from 5 to 8 cm. be -low this point. Sometimes the aorta arches over the root of the right lung (right aortic arch) instead of over that of the left, and passes down on the right side of the vertebral column, a condition which is found in birds. In such cases all the thoracic and abdominal viscera are transposed. Less frequently the aorta, after arching over the root of the right lung, is directed to its usual position on the left side of the vertebral column; this peculiarity is not accompanied by transposition of the viscera. The aorta occasionally divides, as in some quadrupeds, into an ascending and a descending trunk, the former of which is di -rected vertically upward, and subdivides into three branches, to supply the head and upper extremities. Sometimes the aorta subdivides near its origin into two branches, which soon reunite. In one of these cases the esophagus and trachea were found to pass through the interval between the two branches; this is the normal condition of the vessel in the reptilia.

Branches.—The branches given off from the arch of the aorta are three in number: the innominate, the left com-mon carotid, and the left subclavian.

Peculiarities.—Position of the Branches.—The branches, instead of arising from the highest part of the arch, may spring from the commencement of the arch or upper part of the ascending aorta; or the distance between them at their ori -

gins may be increased or diminished, the most frequent change in this respect being the approximation of the left carotid to-ward the innominate artery.

The number of the primary branches may be reduced to one, or more commonly two; the left carotid arising from the innominate artery; or (more rarely) the carotid and subclavian arteries of the left side arising from a left innominate artery. But the number may be increased to four, from the right carotid and subclavian arteries arising directly from the aorta, the innominate being absent. In most of these latter cases the right subclavian has been found to arise from the left end of the arch; in other cases it is the second or third branch given off, instead of the first. Another common form in which there are four primary branches is that in which the left vertebral artery arises from the arch of the aorta between the left carotid and subclavian arteries. Lastly, the number of trunks from the arch may be increased to five or six; in these in-stances, the external and internal carotids arise separately from the arch, the common carotid being absent on one or both sides. In some few cases six branches have been found, and this condition is associated with the origin of both vertebral ar -teries from the arch.

Number Usual, Arrangement Different.—When the aorta arches over to the right side, the three branches have an arrangement the reverse of what is usual; the innominate artery is a left, one, and the right carotid and subclavian arise sep -arately. In other cases, where the aorta takes its usual course, the two carotids may be joined in a common trunk, and the subclavians arise separately from the arch, the right subclavian generally arising from the left end of the arch.

In some instances other arteries spring from the arch of the aorta. Of these the most common are the bronchial, one or both, and the thyreoidea ima; but the internal mammary and the inferior thyroid have been seen to arise from this vessel.

The Subclavian Artery (A. Subclavia).—On the right side the subclavian artery arises from the innominate artery behind the right sternoclavicular articulation; on the left side it springs from the arch of the aorta. The two vessels, therefore, in the first part of their course, differ in length, direction, and relation with neighboring structures.

In order to facilitate the description, each subclavian artery is divided into three parts. The first portion extends from the origin of the vessel to the medial border of the Scalenus anterior; the second lies behind this muscle; and the third ex -tends from the lateral margin of the muscle to the outer border of the first rib, where it becomes the axillary artery. The first portions of the two vessels require separate descriptions; the second and third parts of the two arteries are practically alike.

First Part of the Right Subclavian Artery.—The first part of the right subclavian artery arises from the innomi-nate artery, behind the upper part of the right sternoclavicular articulation, and passes upward and lateralward to the medial margin of the Scalenus anterior. It ascends a little above the clavicle, the extent to which it does so varying in different cases.

Relations.—It is covered, in front, by the integument, superficial fascia, Platysma, deep fascia, the clavicular origin of the Sternocleidomastoideus, the Sternohyoideus, and Sternothyreoideus, and another layer of the deep fascia. It is crossed by the internal jugular and vertebral veins, by the vagus nerve and the cardiac branches of the vagus and sympa -thetic, and by the subclavian loop of the sympathetic trunk which forms a ring around the vessel. The anterior jugular vein is directed lateralward in front of the artery, but is separated from it by the Sternohyoideus and Sternothyreoideus. Below and behind the artery is the pleura, which separates it from the apex of the lung; behind is the sympathetic trunk, the Longus collie and the first thoracic vertebra. The right recurrent nerve winds around the lower and back part of the vessel.

First Part of the Left Subclavian Artery.—The first part of the left subclavian artery arises from the arch of the aorta, behind the left common carotid, and at the level of the fourth thoracic vertebra; it ascends in the superior mediastinal cavity to the root of the neck and then arches lateralward to the medial border of the Scalenus anterior.

Relations.—It is in relation, in front, with the vagus, cardiac, and phrenic nerves, which lie parallel with it, the left common carotid artery, left internal jugular and vertebral veins, and the commencement of the left innominate vein, and is covered by the Sternothyreoideus, Sternohyoideus, and Sternocleidomastoideus; behind, it is in relation with the esophagus, thoracic duct, left recurrent nerve, inferior cervical ganglion of the sympathetic trunk, and Longus colli; higher up, how-ever, the esophagus and thoracic duct lie to its right side; the latter ultimately arching over the vessel to join the angle of union between the subclavian and internal jugular veins. Medial to it are the esophagus, trachea, thoracic duct, and left re-current nerve; lateral to it, the left pleura and lung.

Second and Third Parts of the Subclavian Artery.—The second portion of the subclavian artery lies behind the Scalenus anterior; it is very short, and forms the highest part of the arch described by the vessel.

Relations.—It is covered, in front, by the skin, superficial fascia, Platysma, deep cervical fascia, Sternocleidomas-toideus, and Scalenus anterior. On the right side of the neck the phrenic nerve is separated from the second part of the artery by the Scalenus anterior, while on the left side it crosses the first part of the artery close to the medial edge of the muscle. Behind the vessel are the pleura and the Scalenus medius; above, the brachial plexus of nerves; below, the pleura. The subclavian vein lies below and in front of the artery, separated from it by the Scalenus anterior.

The third portion of the subclavian artery runs downward and lateralward from the lateral margin of the Scalenus anterior to the outer border of the first rib, where it becomes the axillary artery. This is the most superficial portion of the vessel, and is contained in the subclavian triangle.

Relations.—It is covered, in front, by the skin, the superficial fascia, the Platysma, the supraclavicular nerves, and the deep cervical fascia. The external jugular vein crosses its medial part and receives the transverse scapular, transverse cervical, and anterior jugular veins, which frequently form a plexus in front of the artery. Behind the veins, the nerve to the Subclavius descends in front of the artery. The terminal part of the artery lies behind the clavicle and the Subclavius and is crossed by the transverse scapular vessels. The subclavian vein is in front of and at a slightly lower level than the artery. Behind, it lies on the lowest trunk of the brachial plexus, which intervenes between it and the Scalenus medius. Above and to its lateral side are the upper trunks of the brachial plexus and the Omohyoideus. Below, it rests on the upper surface of the first rib.

Peculiarities.—The subclavian arteries vary in their origin, their course, and the height to which they rise in the neck.

The origin of the right subclavian from the innominate takes place, in some cases, above the sternoclavicular articu-lation, and occasionally, but less frequently, below that joint. The artery may arise as a separate trunk from the arch of the aorta, and in such cases it may be either the first, second, third, or even the last branch derived from that vessel; in the ma -jority, however, it is the first or last, rarely the second or third. When it is the first branch, it occupies the ordinary position of the innominate artery; when the second or third, it gains its usual position by passing behind the right carotid; and when the last branch, it arises from the left extremity of the arch, and passes obliquely toward the right side, usually behind the trachea, esophagus, and right carotid, sometimes between the esophagus and trachea, to the upper border of the first rib, whence it follows its ordinary course. In very rare instances, this vessel arises from the thoracic aorta, as low down as the fourth thoracic vertebra. Occasionally, it perforates the Scalenus anterior; more rarely it passes in front of that muscle. Sometimes the subclavian vein passes with the artery behind the Scalenus anterior. The artery may ascend as high as 4 cm. above the clavicle, or any intermediate point between this and the upper border of the bone, the right subclavian usually as -cending higher than the left.

The left subclavian is occasionally joined at its origin with the left carotid.The left subclavian artery is more deeply placed than the right in the first part of its course, and, as a rule, does not

reach quite as high a level in the neck. The posterior border of the Sternocleidomastoideus corresponds pretty closely to the lateral border of the Scalenus anterior, so that the third portion of the artery, the part most accessible for operation, lies im -mediately lateral to the posterior border of the Sternocleidomastoideus.

Collateral Circulation.—After ligature of the third part of the subclavian artery, the collateral circulation is estab-lished mainly by three sets of vessels, thus described in a dissection:

1. A posterior set, consisting of the transverse scapular and the descending ramus of the transverse cervical branches of the subclavian, anastomosing with the subscapular from the axillary.

2. A medial set, produced by the connection of the internal mammary on the one hand, with the highest intercostal and lateral thoracic arteries, and the branches from the subscapular on the other.

3. A middle or axillary set, consisting of a number of small vessels derived from branches of the subclavian, above, and, passing through the axilla, terminating either in the main trunk, or some of the branches of the axillary below. This last set presented most conspicuously the peculiar character of newly formed or, rather, dilated arteries, being excessively tortu-ous, and forming a complete plexus.

The chief agent in the restoration of the axillary artery below the tumor was the subscapular artery, which communi-cated most freely with the internal mammary, transverse scapular and descending ramus of the transverse cervical branches of the subclavian, from all of which it received so great an influx of blood as to dilate it to three times its natural size.

When a ligature is applied to the first part of the subclavian artery, the collateral circulation is carried on by: (1) the anastomosis between the superior and inferior thyroids; (2) the anastomosis of the two vertebrals; (3) the anastomosis of the internal mammary with the inferior epigastric and the aortic intercostals; (4) the costocervical anastomosing with the aortic intercostals; (5) the profunda cervicis anastomosing with the descending branch of the occipital; (6) the scapular branches of the thyrocervical trunk anastomosing with the branches of the axillary, and (7) the thoracic branches of the axillary anas -tomosing with the aortic intercostals.

Branches.—The branches of the subclavian artery are: Vertebral, Internal mammary, Thyrocervical, Costocervical.On the left side all four branches generally arise from the first portion of the vessel; but on the right side the costo-

cervical trunk usually springs from the second portion of the vessel. On both sides of the neck, the first three branches arise close together at the medial border of the Scalenus anterior; in the majority of cases, a free interval of from 1.25 to 2.5 cm. exists between the commencement of the artery and the origin of the nearest branch.

1. The vertebral artery (a. vertebralis), is the first branch of the subclavian, and arises from the upper and back part of the first portion of the vessel. It is surrounded by a plexus of nerve fibers derived from the inferior cervical ganglion of the sympathetic trunk, and ascends through the foramina in the transverse processes of the upper six cervical vertebrae it then winds behind the superior articular process of the atlas and, entering the skull through the foramen magnum, unites, at the lower border of the pons, with the vessel of the opposite side to form the basilar artery.

Relations.—The vertebral artery may be divided into four parts: The first part runs upward and backward between the Longus colli and the Scalenus anterior. In front of it are the internal jugular and vertebral veins, and it is crossed by the inferior thyroid artery; the left vertebral is crossed by the thoracic duct also. Behind it are the transverse process of the sev -enth cervical vertebra, the sympathetic trunk and its inferior cervical ganglion. The second part runs upward through the foramina in the transverse processes of the upper six cervical vertebrae, and is surrounded by branches from the inferior cervical sympathetic ganglion and by a plexus of veins which unite to form the vertebral vein at the lower part of the neck. It is situated in front of the trunks of the cervical nerves, and pursues an almost vertical course as far as the transverse process of the atlas, above which it runs upward and lateralward to the foramen in the transverse process of the atlas. The third part issues from the latter foramen on the medial side of the Rectus capitis lateralis, and curves backward behind the superior articular process of the atlas, the anterior ramus of the first cervical nerve being on its medial side; it then lies in the groove on the upper surface of the posterior arch of the atlas, and enters the vertebral canal by passing beneath the pos-terior atlantoöccipital membrane. This part of the artery is covered by the Semispinalis capitis and is contained in the sub-occipital triangle—a triangular space bounded by the Rectus capitis posterior major, the Obliquus superior, and the Obliquus inferior. The first cervical or suboccipital nerve lies between the artery and the posterior arch of the atlas. The fourth part pierces the dura mater and inclines medialward to the front of the medulla oblongata; it is placed between the hypoglossal nerve and the anterior root of the first cervical nerve and beneath the first digitation of the ligamentum denticu-latum. At the lower border of the pons it unites with the vessel of the opposite side to form the basilar artery.

Branches.—The branches of the vertebral artery may be divided into two sets: those given off in the neck, and those within the cranium.

Cervical Branches. Spinal. Meningeal. Muscular.Cranial Branches. Posterior Spinal. Anterior Spinal. Posterior Inferior Cerebellar. Medullary.Spinal Branches (rami spinales) enter the vertebral canal through the intervertebral foramina, and each divides into

two branches. Of these, one passes along the roots of the nerves to supply the medulla spinalis and its membranes, anasto -mosing with the other arteries of the medulla spinalis; the other divides into an ascending and a descending branch, which unite with similar branches from the arteries above and below, so that two lateral anastomotic chains are formed on the pos-terior surfaces of the bodies of the vertebrae, near the attachment of the pedicles. From these anastomotic chains branches are supplied to the periosteum and the bodies of the vertebrae, and others form communications with similar branches from the opposite side; from these communications small twigs arise which join similar branches above and below, to form a central anastomotic chain on the posterior surface of the bodies of the vertebrae.

Muscular Branches are given off to the deep muscles of the neck, where the vertebral artery curves around the ar -ticular process of the atlas. They anastomose with the occipital, and with the ascending and deep cervical arteries.

The Meningeal Branch (ramus meningeus; posterior meningeal branch) springs from the vertebral opposite the foramen magnum, ramifies between the bone and dura mater in the cerebellar fossa, and supplies the falx cerebelli. It is fre -quently represented by one or two small branches.

The Posterior Spinal Artery (a. spinalis posterior; dorsal spinal artery) arises from the vertebral, at the side of the medulla oblongata; passing backward, it descends on this structure, lying in front of the posterior roots of the spinal nerves, and is reinforced by a succession of small branches, which enter the vertebral canal through the intervertebral foramina; by means of these it is continued to the lower part of the medulla spinalis, and to the cauda equina. Branches from the poste -rior spinal arteries form a free anastomosis around the posterior roots of the spinal nerves, and communicate, by means of very tortuous transverse branches, with the vessels of the opposite side. Close to its origin each gives off an ascending branch, which ends at the side of the fourth ventricle.

The Anterior Spinal Artery (a. spinalis anterior; ventral spinal artery) is a small branch, which arises near the ter-mination of the vertebral, and, descending in front of the medulla oblongata, unites with its fellow of the opposite side at the level of the foramen magnum. One of these vessels is usually larger than the other, but occasionally they are about equal in size. The single trunk, thus formed, descends on the front of the medulla spinalis, and is reinforced by a succession of small branches which enter the vertebral canal through the intervertebral foramina; these branches are derived from the vertebral and the ascending cervical of the inferior thyroid in the neck; from the intercostals in the thorax; and from the lumbar, iliolumbar, and lateral sacral arteries in the abdomen and pelvis. They unite, by means of ascending and descending branches, to form a single anterior median artery, which extend as far as the lower part of the medulla spinalis, and is con-tinued as a slender twig on the filum terminale. This vessel is placed in the pia mater along the anterior median fissure; it supplies that membrane, and the substance of the medulla spinalis, and sends off branches at its lower part to be distributed to the cauda equina.

The Posterior Inferior Cerebellar Artery (a. cerebelli inferior posterior), the largest branch of the vertebral, winds backward around the upper part of the medulla oblongata, passing between the origins of the vagus and accessory nerves, over the inferior peduncle to the under surface of the cerebellum, where it divides into two branches. The medial branch is continued backward to the notch between the two hemispheres of the cerebellum; while the lateral supplies the under surface of the cerebellum, as far as its lateral border, where it anastomoses with the anterior inferior cerebellar and the superior cerebellar branches of the basilar artery. Branches from this artery supply the choroid plexus of the fourth ven-tricle.

The Medullary Arteries (bulbar arteries) are several minute vessels which spring from the vertebral and its branches and are distributed to the medulla oblongata.

The Basilar Artery (a. basilaris), so named from its position at the base of the skull, is a single trunk formed by the junction of the two vertebral arteries: it extends from the lower to the upper border of the pons, lying in its median groove, under cover of the arachnoid. It ends by dividing into the two posterior cerebral arteries.

Its branches, on either side, are the following: Pontine. Anterior Inferior Cerebellar. Internal Auditory. Superior Cerebellar. Posterior Cerebral.

The pontine branches (rami ad pontem; transverse branches) are a number of small vessels which come off at right angles from either side of the basilar artery and supply the pons and adjacent parts of the brain.

The internal auditory artery (a. auditiva interna; auditory artery), a long slender branch, arises from near the middle of the artery; it accompanies the acoustic nerve through the internal acoustic meatus, and is distributed to the inter-nal ear.

The anterior inferior cerebellar artery (a. cerebelli inferior anterior) passes backward to be distributed to the an-terior part of the under surface of the cerebellum, anastomosing with the posterior inferior cerebellar branch of the verte -bral.

The superior cerebellar artery (a. cerebelli superior) arises near the termination of the basilar. It passes lateral-ward, immediately below the oculomotor nerve, which separates it from the posterior cerebral artery, winds around the cerebral peduncle, close to the trochlear nerve, and, arriving at the upper surface of the cerebellum, divides into branches which ramify in the pia mater and anastomose with those of the inferior cerebellar arteries. Several branches are given to the pineal body, the anterior medullary velum, and the tela chorioidea of the third ventricle.

The posterior cerebral artery (a. cerebri posterior) is larger than the preceding, from which it is separated near its origin by the oculomotor nerve. Passing lateralward, parallel to the superior cerebellar artery, and receiving the posterior

communicating from the internal carotid, it winds around the cerebral peduncle, and reaches the tentorial surface of the oc-cipital lobe of the cerebrum, where it breaks up into branches for the supply of the temporal and occipital lobes.

The branches of the posterior cerebral artery are divided into two sets, ganglionic and cortical:Ganglionic - Posterior-medial.Cortical - Anterior Temporal, Posterior Choroidal, Posterior Temporal, Postero-lateral, Calcarine, Parietoöccipital.Ganglionic.—The postero-medial ganglionic branches are a group of small arteries which arise at the commence-

ment of the posterior cerebral artery: these, with similar branches from the posterior communicating, pierce the posterior perforated substance, and supply the medial surfaces of the thalami and the walls of the third ventricle. The posterior choroidal branches run forward beneath the splenium of the corpus callosum, and supply the tela chorioidea of the third ventricle and the choroid plexus. The postero-lateral ganglionic branches are small arteries which arise from the poste-rior cerebral artery after it has turned around the cerebral peduncle; they supply a considerable portion of the thalamus.

Cortical.—The cortical branches are: the anterior temporal, distributed to the uncus and the anterior part of the fusiform gyrus; the posterior temporal, to the fusiform and the inferior temporal gyri; the calcarine, to the cuneus and gyrus lingualis and the back part of the convex surface of the occipital lobe; and the parietoöccipital, to the cuneus and the precuneus.

2. The thyrocervical trunk (truncus thyreocervicalis; thyroid axis) is a short thick trunk, which arises from the front of the first portion of the subclavian artery, close to the medial border of the Scalenus anterior, and divides almost im -mediately into three branches, the inferior thyroid, transverse scapular, and transverse cervical.

The Inferior Thyroid Artery (a. thyreoidea inferior) passes upward, in front of the vertebral artery and Longus colli; then turns medialward behind the carotid sheath and its contents, and also behind the sympathetic trunk, the middle cervical ganglion resting upon the vessel. Reaching the lower border of the thyroid gland it divides into two branches, which supply the postero-inferior parts of the gland, and anastomose with the superior thyroid, and with the corresponding artery of the opposite side. The recurrent nerve passes upward generally behind, but occasionally in front, of the artery.

The branches of the inferior thyroid are: Inferior Laryngeal, Esophageal, Tracheal, Ascending Cervical, Muscular.The inferior laryngeal artery (a. laryngea inferior) ascends upon the trachea to the back part of the larynx under

cover of the Constrictor pharyngis inferior, in company with the recurrent nerve, and supplies the muscles and mucous membrane of this part, anastomosing with the branch from the opposite side, and with the superior laryngeal branch of the superior thyroid artery.

The tracheal branches (rami tracheales) are distributed upon the trachea, and anastomose below with the bronchial arteries.

The esophageal branches (rami aesophagei) supply the esophagus, and anastomose with the esophageal branches of the aorta.

The ascending cervical artery (a. cervicalis ascendens) is a small branch which arises from the inferior thyroid as that vessel is passing behind the carotid sheath; it runs up on the anterior tubercles of the transverse processes of the cervi-cal vertebrae in the interval between the Scalenus anterior and Longus capitis. To the muscles of the neck it gives twigs which anastomose with branches of the vertebral, and it sends one or two spinal branches into the vertebral canal through the intervertebral foramina to be distributed to the medulla spinalis and its membranes, and to the bodies of the vertebrae, in the same manner as the spinal branches from the vertebral. It anastomoses with the ascending pharyngeal and occipital ar-teries.

The muscular branches supply the depressors of the hyoid bone, and the Longus colli, Scalenus anterior, and Con-strictor pharyngis inferior.

The Transverse Scapular Artery (a. transversa scapulae suprascapular artery) passes at first downward and later-alward across the Scalenus anterior and phrenic nerve, being covered by the Sternocleidomastoideus; it then crosses the subclavian artery and the brachial plexus, and runs behind and parallel with the clavicle and Subclavius, and beneath the in-ferior belly of the Omohyoideus, to the superior border of the scapula; it passes over the superior transverse ligament of the scapula which separates it from the suprascapular nerve, and enters the supraspinatous fossa. In this situation it lies close to the bone, and ramifies between it and the Supraspinatus, to which it supplies branches. It then descends behind the neck of the scapula, through the great scapular notch and under cover of the inferior transverse ligament, to reach the infraspinatous fossa, where it anastomoses with the scapular circumflex and the descending branch of the transverse cervical. Besides dis -tributing branches to the Sternocleidomastoideus, Subclavius, and neighboring muscles, it gives off a suprasternal branch, which crosses over the sternal end of the clavicle to the skin of the upper part of the chest; and an acromial branch, which pierces the Trapezius and supplies the skin over the acromion, anastomosing with the thoracoacromial artery. As the artery passes over the superior transverse ligament of the scapula, it sends a branch into the subscapular fossa, where it ramifies beneath the Subscapularis, and anastomoses with the subscapular artery and with the descending branch of the transverse cervical. It also sends articular branches to the acromioclavicular and shoulder-joints, and a nutri -ent artery to the clavicle.

The Transverse Cervical Artery (a. transversa colli; transversalis colli artery) lies at a higher level than the trans-verse scapular; it passes transversely above the inferior belly of the Omohyoideus to the anterior margin of the Trapezius, beneath which it divides into an ascending and a descending branch. It crosses in front of the phrenic nerve and the Scaleni, and in front of or between the divisions of the brachial plexus, and is covered by the Platysma and Sternocleido -mastoideus, and crossed by the Omohyoideus and Trapezius.

The ascending branch (ramus ascendens; superficial cervical artery) ascends beneath the anterior margin of the Trapezius, distributing branches to it, and to the neighboring muscles and lymph glands in the neck, and anastomosing with the superficial branch of the descending ramus of the occipital artery.

The descending branch (ramus descendens; posterior scapular artery) passes beneath the Levator scapulae to the medial angle of the scapula, and then descends under the Rhomboidei along the vertebral border of that bone as far as the inferior angle. It supplies the Rhomboidei, Latissimus dorsi and Trapezius, and anastomoses with the transverse scapular and subscapular arteries, and with the posterior branches of some of the intercostal arteries.

Peculiarities.—The ascending branch of the transverse cervical frequently arises directly from the thyrocervical trunk; and the descending branch from the third, more rarely from the second, part of the subclavian.

3. The internal mammary artery (a. mammaria interna) arises from the under surface of the first portion of the subclavian, opposite the thyrocervical trunk. It descends behind the cartilages of the upper six ribs at a distance of about 1.25 cm. from the margin of the sternum, and at the level of the sixth intercostal space divides into the musculophrenic and superior epigastric arteries.

Relations.—It is directed at first downward, forward, and medialward behind the sternal end of the clavicle, the subclavian and internal jugular veins, and the first costal cartilage, and passes forward close to the lateral side of the innom-inate vein. As it enters the thorax the phrenic nerve crosses from its lateral to its medial side. Below the first costal cartilage it descends almost vertically to its point of bifurcation. It is covered in front by the cartilages of the upper six ribs and the intervening Intercostales interni and anterior intercostal membranes, and is crossed by the terminal portions of the upper six intercostal nerves. It rests on the pleura, as far as the third costal cartilage; below this level, upon the Transversus thoracis. It is accompanied by a pair of veins; these unite above to form a single vessel, which runs medial to the artery and ends in the corresponding innominate vein.

Branches.—The branches of the internal mammary are: Pericardiacophrenic, Intercostal, Anterior Mediastinal, Per-forating, Pericardial, Musculophrenic, Sternal, Superior Epigastric.

The Pericardiacophrenic Artery (a. pericardiacophrenica; a. comes nervi phrenici) is a long slender branch, which accompanies the phrenic nerve, between the pleura and pericardium, to the diaphragm, to which it is distributed; it anastomoses with the musculophrenic and inferior phrenic arteries.

The Anterior Mediastinal Arteries (aa. mediastinales anteriores; mediastinal arteries) are small vessels, distrib-uted to the areolar tissue and lymph glands in the anterior mediastinal cavity, and to the remains of the thymus.

The Pericardial Branches supply the upper part of the anterior surface of the pericardium; the lower part receives branches from the musculophrenic artery.

The Sternal Branches (rami sternales) are distributed to the Transversus thoracis, and to the posterior surface of the sternum.

The anterior mediastinal, pericardial, and sternal branches, together with some twigs from the pericardiacophrenic, anastomose with branches from the intercostal and bronchial arteries, and form a subpleural mediastinal plexus.

The Intercoastal Branches (rami intercostales; anterior intercostal arteries) supply the upper five or six intercostal spaces. Two in number in each space, these small vessels pass lateralward, one lying near the lower margin of the rib above, and the other near the upper margin of the rib below, and anastomose with the intercostal arteries from the aorta. They are at first situated between the pleura and the Intercostales interni, and then between the Intercostales interni and ex-terni. They supply the Intercostales and, by branches which perforate the Intercostales externi, the Pectorales and the mamma.

The Perforating Branches (rami perforantes) correspond to the five or six intercostal spaces. They pass forward through the intercostal spaces, and, curving lateralward, supply the Pectoralis major and the integument. Those which cor-respond to the second, third, and fourth spaces give branches to the mamma, and during lactation are of large size.

The Musculophrenic Artery (a. musculophrenica) is directed obliquely downward and lateralward, behind the car-tilages of the false ribs; it perforates the diaphragm at the eighth or ninth costal cartilage, and ends, considerably reduced in size, opposite the last intercostal space. It gives off intercostal branches to the seventh, eighth, and ninth intercostal spaces; these diminish in size as the spaces decrease in length, and are distributed in a manner precisely similar to the intercostals from the internal mammary. The musculophrenic also gives branches to the lower part of the pericardium, and others which run backward to the diaphragm, and downward to the abdominal muscles.

The Superior Epigastric Artery (a. epigastrica superior) continues in the original direction of the internal mam-mary; it descends through the interval between the costal and sternal attachments of the diaphragm, and enters the sheath of the Rectus abdominis, at first lying behind the muscle, and then perforating and supplying it, and anastomosing with the in-ferior epigastric artery from the external iliac. Branches perforate the anterior wall of the sheath of the Rectus, and supply the muscles of the abdomen and the integument, and a small branch passes in front of the xiphoid process and anastomoses with the artery of the opposite side. It also gives some twigs to the diaphragm, while from the artery of the right side small branches extend into the falciform ligament of the liver and anastomose with the hepatic artery.

4. The costocervical trunk (truncus costocervicalis; superior intercostal artery) arises from the upper and back part of the subclavian artery, behind the Scalenus anterior on the right side, and medial to that muscle on the left side. Pass-ing backward, it gives off the profunda cervicalis, and, continuing as the highest intercostal artery, descends behind the pleura in front of the necks of the first and second ribs, and anastomoses with the first aortic intercostal. As it crosses the neck of the first rib it lies medial to the anterior division of the first thoracic nerve, and lateral to the first thoracic ganglion of the sympathetic trunk.

In the first intercostal space, it gives off a branch which is distributed in a manner similar to the distribution of the aortic intercostals. The branch for the second intercostal space usually joins with one from the highest aortic intercostal artery. This branch is not constant, but is more commonly found on the right side; when absent, its place is supplied by an intercostal branch from the aorta. Each intercostal gives off a posterior branch which goes to the posterior vertebral mus-cles, and sends a small spinal branch through the corresponding intervertebral foramen to the medulla spinalis and its mem-branes.

The Profunda Cervicalis (a. cervicalis profunda; deep cervical branch) arises, in most cases, from the costocervi-cal trunk, and is analogous to the posterior branch of an aortic intercostal artery: occasionally it is a separate branch from the subclavian artery. Passing backward, above the eighth cervical nerve and between the transverse process of the seventh cervical vertebra and the neck of the first rib, it runs up the back of the neck, between the Semispinales capitis and colli, as high as the axis vertebra, supplying these and adjacent muscles, and anastomosing with the deep division of the descending branch of the occipital, and with branches of the vertebral. It gives off a spinal twig which enters the canal through the in-tervertebral foramen between the seventh cervical and first thoracic vertebrae.

Note. The vertebral artery sometimes enters the foramen in the transverse process of the fifth vertebra, and has been seen entering that of the seventh vertebra.

The Common Carotid ArteryThe principal arteries of supply to the head and neck are the two common carotids; they ascend in the neck and

each divides into two branches, viz., (1) the external carotid, supplying the exterior of the head, the face, and the greater part of the neck; (2) the internal carotid, supplying to a great extent the parts within the cranial and orbital cavities.

The Common Carotid Artery (A. Carotis Communis)—The common carotid arteries differ in length and in their mode of origin. The right begins at the bifurcation of the innominate artery behind the sternoclavicular joint and is confined to the neck. The left springs from the highest part of the arch of the aorta to the left of, and on a plane posterior to the innominate artery, and therefore consists of a thoracic and a cervical portion.

The thoracic portion of the left common carotid artery ascends from the arch of the aorta through the superior mediastinum to the level of the left sternoclavicular joint, where it is continuous with the cervical portion.

1. Relations.—In front, it is separated from the manubrium sterni by the Sternohyoideus and Sternothyreoideus, the anterior portions of the left pleura and lung, the left innominate vein, and the remains of the thymus; behind, it lies on the trachea, esophagus, left recurrent nerve, and thoracic duct. To its right side below is the innominate artery, and above, the trachea, the inferior thyroid veins, and the remains of the thymus; to its left side are the left vagus and phrenic nerves, left pleura, and lung. The left subclavian artery is posterior and slightly lateral to it.

The cervical portions of the common carotids resemble each other so closely that one description will apply to both. Each vessel passes obliquely upward, from behind the sternoclavicular articulation, to the level of the upper border of the thyroid cartilage, where it divides into the external and internal carotid arteries.

At the lower part of the neck the two common carotid arteries are separated from each other by a very narrow in-terval which contains the trachea; but at the upper part, the thyroid gland, the larynx and pharynx project forward between the two vessels. The common carotid artery is contained in a sheath, which is derived from the deep cervical fascia and en-closes also the internal jugular vein and vagus nerve, the vein lying lateral to the artery, and the nerve between the artery and vein, on a plane posterior to both. On opening the sheath, each of these three structures is seen to have a separate fi-brous investment.

Relations.—At the lower part of the neck the common carotid artery is very deeply seated, being covered by the integument, superficial fascia, Platysma, and deep cervical fascia, the Sternocleidomastoideus, Sternohyoideus, Ster-nothyreoideus, and Omohyoideus; in the upper part of its course it is more superficial, being covered merely by the integu-ment, the superficial fascia, Platysma, deep cervical fascia, and medial margin of the Sternocleidomastoideus. When the latter muscle is drawn backward, the artery is seen to be contained in a triangular space, the carotid triangle, bounded be-hind by the Sternocleidomastoideus, above by the Stylohyoideus and posterior belly of the Digastricus, and below by the superior belly of the Omohyoideus. This part of the artery is crossed obliquely, from its medial to its lateral side, by the sternocleidomastoid branch of the superior thyroid artery; it is also crossed by the superior and middle thyroid veins which end in the internal jugular; descending in front of its sheath is the descending branch of the hypoglossal nerve, this filament being joined by one or two branches from the cervical nerves, which cross the vessel obliquely. Sometimes the descending branch of the hypoglossal nerve is contained within the sheath. The superior thyroid vein crosses the artery near its termina-tion, and the middle thyroid vein a little below the level of the cricoid cartilage; the anterior jugular vein crosses the artery just above the clavicle, but is separated from it by the Sternohyoideus and Sternothyreoideus. Behind, the artery is sepa-rated from the transverse processes of the cervical vertebrae by the Longus colli and Longus capitis, the sympathetic trunk being interposed between it and the muscles. The inferior thyroid artery crosses behind the lower part of the vessel. Medi-ally, it is in relation with the esophagus, trachea, and thyroid gland (which overlaps it), the inferior thyroid artery and recur-rent nerve being interposed; higher up, with the larynx and pharynx. Lateral to the artery are the internal jugular vein and vagus nerve.

At the lower part of the neck, the right recurrent nerve crosses obliquely behind the artery; the right internal jugu-lar vein diverges from the artery, but the left approaches and often overlaps the lower part of the artery.

Behind the angle of bifurcation of the common carotid artery is a reddish-brown oval body, known as the glomus caroticum (carotid body). It is similar in structure to the glomus coccygeum (coccygeal body) which is situated on the middle sacral artery.

Peculiarities as to Origin.—The right common carotid may arise above the level of the upper border of the stern-oclavicular articulation; this variation occurs in about 12 per cent. of cases. In other cases the artery may arise as a separate branch from the arch of the aorta, or in conjunction with the left carotid. The left common carotid varies in its origin more than the right. In the majority of abnormal cases it arises with the innominate artery; if that artery is absent, the two carotids arise usually by a single trunk. It is rarely joined with the left subclavian, except in cases of transposition of the aortic arch.

Peculiarities as to Point of Division.—In the majority of abnormal cases this occurs higher than usual, the artery dividing opposite or even above the hyoid bone; more rarely, it occurs below, opposite the middle of the larynx, or the lower border of the cricoid cartilage; one case is related by Morgagni, where the artery was only 4 cm. in length and di-vided at the root of the neck. Very rarely, the common carotid ascends in the neck without any subdivision, either the exter-

nal or the internal carotid being wanting; and in a few cases the common carotid has been found to be absent, the external and internal carotids arising directly from the arch of the aorta. This peculiarity existed on both sides in some instances, on one side in others.

Occasional Branches.—The common carotid usually gives off no branch previous to its bifurcation, but it occa-sionally gives origin to the superior thyroid or its laryngeal branch, the ascending pharyngeal, the inferior thyroid, or, more rarely, the vertebral artery.

Collateral Circulation.—After ligature of the common carotid, the collateral circulation can be perfectly estab-lished, by the free communication which exists between the carotid arteries of opposite sides, both without and within the cranium, and by enlargement of the branches of the subclavian artery on the side corresponding to that on which the vessel has been tied. The chief communications outside the skull take place between the superior and inferior thyroid arteries, and the profunda cervicis and ramus descendens of the occipital; the vertebral takes the place of the internal carotid within the cranium.

Practice skillsStudents are supposed to identify the following structures on the samples:

Aorta - aortic bulb- ascending aorta- arch of aorta- branches of aortic arch- descending aorta- thoracic aortaBrachiocephalic trunk - right common carotid artery- right subclavian arteryCommon carotid artery (right, left)

Subclavian artery (right, left) - vertebral artery- basilar artery- posterior cerebral artery- internal thoracic artery- thyrocervical trunk- inferior thyroid artery- costocervical trunk- transverse cervical artery- cerebral arterial circle

Practice class 13. The internal carotid arteries: relations, anastomoses, branches. The sup-plement of the brain and meninges.

The aim: to learn the characteristic of the internal carotid artery, to learn its topography, branches and area of blood supply.

Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-sents special interest for therapists.

The plan of the practice class:A. Checking of the home assignment: oral quiz or written test control – 30 minutes.B. Summary lecture on the topic by teacher – 30 minutes.

a) The course and relations of the internal carotid artery.b) The branches of the internal carotid artery.c) Blood supply of the brain and meninges.

C. Students’ self-taught time – 55 minutesD. Home-task – 5 minutes

The Internal Carotid Artery (A. Carotis Interna)The internal carotid artery supplies the anterior part of the brain, the eye and its appendages, and sends branches to

the forehead and nose. Its size, in the adult, is equal to that of the external carotid, though, in the child, it is larger than that vessel. It is remarkable for the number of curvatures that it presents in different parts of its course. It occasionally has one or two flexures near the base of the skull, while in its passage through the carotid canal and along the side of the body of the sphenoid bone it describes a double curvature and resembles the italic letter S.

Course and Relations.—In considering the course and relations of this vessel it may be divided into four portions: cervical, petrous, cavernous, and cerebral.

Cervical Portion.—This portion of the internal carotid begins at the bifurcation of the common carotid, opposite the upper border of the thyroid cartilage, and runs perpendicularly upward, in front of the transverse processes of the upper three cervical vertebrae, to the carotid canal in the petrous portion of the temporal bone. It is comparatively superficial at its commencement, where it is contained in the carotid triangle, and lies behind and lateral to the external carotid, overlapped by the Sternocleidomastoideus, and covered by the deep fascia, Platysma, and integument: it then passes beneath the parotid gland, being crossed by the hypoglossal nerve, the Digastricus and Stylohyoideus, and the occipital and posterior auricular arteries. Higher up, it is separated from the external carotid by the Styloglossus and Stylopharyngeus, the tip of the styloid process and the stylohyoid ligament, the glossopharyngeal nerve and the pharyngeal branch of the vagus. It is in relation, behind, with the Longus capitis, the superior cervical ganglion of the sympathetic trunk, and the superior laryngeal nerve; laterally, with the internal jugular vein and vagus nerve, the nerve lying on a plane posterior to the artery; medially,

with the pharynx, superior laryngeal nerve, and ascending pharyngeal artery. At the base of the skull the glossopharyngeal, vagus, accessory, and hypoglossal nerves lie between the artery and the internal jugular vein.

Petrous Portion.—When the internal carotid artery enters the canal in the petrous portion of the temporal bone, it first ascends a short distance, then curves forward and medialward, and again ascends as it leaves the canal to enter the cav-ity of the skull between the lingula and petrosal process of the sphenoid. The artery lies at first in front of the cochlea and tympanic cavity; from the latter cavity it is separated by a thin, bony lamella, which is cribriform in the young subject, and often partly absorbed in old age. Farther forward it is separated from the semilunar ganglion by a thin plate of bone, which forms the floor of the fossa for the ganglion and the roof of the horizontal portion of the canal. Frequently this bony plate is more or less deficient, and then the ganglion is separated from the artery by fibrous membrane. The artery is separated from the bony wall of the carotid canal by a prolongation of dura mater, and is surrounded by a number of small veins and by fil-aments of the carotid plexus, derived from the ascending branch of the superior cervical ganglion of the sympathetic trunk.

Cavernous Portion.—In this part of its course, the artery is situated between the layers of the dura mater forming the cavernous sinus, but covered by the lining membrane of the sinus. It at first ascends toward the posterior clinoid process, then passes forward by the side of the body of the sphenoid bone, and again curves upward on the medial side of the anterior clinoid process, and perforates the dura mater forming the roof of the sinus. This portion of the artery is sur-rounded by filaments of the sympathetic nerve, and on its lateral side is the abducent nerve.

Cerebral Portion.—Having perforated the dura mater on the medial side of the anterior clinoid process, the internal carotid passes between the optic and oculomotor nerves to the anterior perforated substance at the medial extremity of the lateral cerebral fissure, where it gives off its terminal or cerebral branches.

Peculiarities.—The length of the internal carotid varies according to the length of the neck, and also according to the point of bifurcation of the common carotid. It arises sometimes from the arch of the aorta; in such rare instances, this vessel has been found to be placed nearer the middle line of the neck than the external carotid, as far upward as the larynx, when the latter vessel crossed the internal carotid. The course of the artery, instead of being straight, may be very tortuous. A few instances are recorded in which this vessel was altogether absent; in one of these the common carotid passed up the neck, and gave off the usual branches of the external carotid; the cranial portion of the internal carotid was replaced by two branches of the internal maxillary, which entered the skull through the foramen rotundum and foramen ovale, and joined to form a single vessel.

Branches.—The cervical portion of the internal carotid gives off no branches. Those from the other portions are:From the Petrous Portion – Caroticotympanic, Artery of the Pterygoid Canal.From the Cavernous Portion – Cavernous, Hypophyseal, Semilunar, Anterior Meningeal, Ophthalmic.From the Cerebral Portion - Anterior Cerebral, Middle Cerebral, Posterior Communicating, Choroidal.1. The caroticotympanic branch (ramus caroticotympanicus; tympanic branch) is small; it enters the tympanic

cavity through a minute foramen in the carotid canal, and anastomoses with the anterior tympanic branch of the internal maxillary, and with the stylomastoid artery.

2. The artery of the pterygoid canal (a. canilis pterygoidei [Vidii]; Vidian artery) is a small, inconstant branch which passes into the pterygoid canal and anastomoses with a branch of the internal maxillary artery.

3. The cavernous branches are numerous small vessels which supply the hypophysis, the semilunar ganglion, and the walls of the cavernous and inferior petrosal sinuses. Some of them anastomose with branches of the middle meningeal.

4. The hypophyseal branches are one or two minute vessels supplying the hypophysis.5. The semilunar branches are small vessels to the semilunar ganglion.6. The anterior meningeal branch (a. meningea anterior) is a small branch which passes over the small wing of the

sphenoid to supply the dura mater of the anterior cranial fossa; it anastomoses with the meningeal branch from the posterior ethmoidal artery.

7. The ophthalmic artery (a. ophthalmica) (Fig. 514) arises from the internal carotid, just as that vessel is emerging from the cavernous sinus, on the medial side of the anterior clinoid process, and enters the orbital cavity through the optic foramen, below and lateral to the optic nerve. It then passes over the nerve to reach the medial wall of the orbit, and thence horizontally forward, beneath the lower border of the Obliquus superior, and divides it into two terminal branches, the frontal and dorsal nasal. As the artery crosses the optic nerve it is accompanied by the nasociliary nerve, and is separated from the frontal nerve by the Rectus superior and Levator palpebrae superioris.

Branches.—The branches of the ophthalmic artery may be divided into an orbital group, distributed to the orbit and surrounding parts; and an ocular group, to the muscles and bulb of the eye.

Orbital Group - Lacrimal. Supraorbital. Posterior Ethmoidal. Anterior Ethmoidal. Medial Palpebral. Frontal. Dorsal Nasal.

Ocular Group - Central Artery of the Retina. Short Posterior Ciliary. Long Posterior Ciliary. Anterior Ciliary. Mus-cular.

The Lacrimal Artery (a. lacrimalis) arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic: not infrequently it is given off before the artery enters the orbit. It accompanies the lacrimal nerve along the upper border of the Rectus lateralis, and supplies the lacrimal gland. Its terminal branches, escaping from the gland, are distributed to the eyelids and conjunctiva: of those supplying the eyelids, two are of considerable size and are named the lateral palpebral arteries; they run medialward in the upper and lower lids respectively and anastomose with the medial palpebral arteries, forming an arterial circle in this situation. The lacrimal artery give off one or two zygomatic branches, one of which passes through the zygomatico-temporal foramen, to reach the temporal fossa, and anastomoses with the deep temporal arteries; another appears on the cheek through the zygomatico-facial foramen, and anastomoses with the transverse facial. A recurrent branch passes backward through the lateral part of the superior orbital fissure to the

dura mater, and anastomoses with a branch of the middle meningeal artery. The lacrimal artery is sometimes derived from one of the anterior branches of the middle meningeal artery.

The Supraorbital Artery (a. supraorbitalis) springs from the ophthalmic as that vessel is crossing over the optic nerve. It passes upward on the medial borders of the Rectus superior and Levator palpebrae, and meeting the supraorbital nerve accompanies it between the periosteum and Levator palpebrae to the supraorbital foramen; passing through this it di-vides into a superficial and a deep branch, which supply the integument, the muscles, and the pericranium of the forehead, anastomosing with the frontal, the frontal branch of the superficial temporal, and the artery of the opposite side. This artery in the orbit supplies the Rectus superior and the Levator palpebrae, and sends a branch across the pulley of the Obliquus su-perior, to supply the parts at the medial palpebral commissure. At the supraorbital foramen it frequently transmits a branch to the diploë.

The Ethmoidal Arteries are two in number: posterior and anterior. The posterior ethmoidal artery, the smaller, passes through the posterior ethmoidal canal, supplies the posterior ethmoidal cells, and, entering the cranium, gives off a meningeal branch to the dura mater, and nasal branches which descend into the nasal cavity through apertures in the cribri-form plate, anastomosing with branches of the sphenopalatine. The anterior ethmoidal artery accompanies the nasociliary nerve through the anterior ethmoidal canal, supplies the anterior and middle ethmoidal cells and frontal sinus, and, entering the cranium, gives off a meningeal branch to the dura mater, and nasal branches; these latter descend into the nasal cavity through the slit by the side of the crista galli, and, running along the groove on the inner surface of the nasal bone, supply branches to the lateral wall and septum of the nose, and a terminal branch which appears on the dorsum of the nose be-tween the nasal bone and the lateral cartilage.

The Medial Palpebral Arteries (aa. palpebrales mediales; internal palpebral arteries), two in number, superior and inferior, arise from the ophthalmic, opposite the pulley of the Obliquus superior; they leave the orbit to encircle the eyelids near their free margins, forming a superior and an inferior arch, which lie between the Orbicularis oculi and the tarsi. The superior palpebral anastomoses, at the lateral angle of the orbit, with the zygomaticoörbital branch of the tem-poral artery and with the upper of the two lateral palpebral branches from the lacrimal artery; the inferior palpebral anas-tomoses, at the lateral angle of the orbit, with the lower of the two lateral palpebral branches from the lacrimal and with the transverse facial artery, and, at the medial part of the lid, with a branch from the angular artery. From this last anastomoses a branch passes to the nasolacrimal duct, ramifying in its mucous membrane, as far as the inferior meatus of the nasal cav-ity.

The Frontal Artery (a. frontalis), one of the terminal branches of the ophthalmic, leaves the orbit at its medial angle with the supratrochlear nerve, and, ascending on the forehead, supplies the integument, muscles, and pericranium, anasto-mosing with the supraorbital artery, and with the artery of the opposite side.

The Dorsal Nasal Artery (a. dorsalis nasi; nasal artery), the other terminal branch of the ophthalmic, emerges from the orbit above the medial palpebral ligament, and, after giving a twig to the upper part of the lacrimal sac, divides into two branches, one of which crosses the root of the nose, and anastomoses with the angular artery, the other runs along the dor-sum of the nose, supplies its outer surface; and anastomoses with the artery of the opposite side, and with the lateral nasal branch of the external maxillary.

The Central Artery of the Retina (a. centralis retinœ) is the first and one of the smallest branches of the oph-thalmic artery. It runs for a short distance within the dural sheath of the optic nerve, but about 1.25 cm. behind the eyeball it pierces the nerve obliquely, and runs forward in the center of its substance to the retina. Its mode of distribution will be de-scribed with the anatomy of the eye.

The Ciliary Arteries (aa. ciliares) are divisible into three groups, the long and short, posterior, and the anterior. The short posterior ciliary arteries from six to twelve in number, arise from the ophthalmic, or its branches; they pass forward around the optic nerve to the posterior part of the eyeball, pierce the sclera around the entrance of the nerve, and supply the choroid and ciliary processes. The long posterior ciliary arteries, two in number, pierce the posterior part of the sclera at some little distance from the optic nerve, and run forward, along either side of the eyeball, between the sclera and choroid, to the ciliary muscle, where they divide into two branches; these form an arterial circle, the circulus arteriosus major, around the circumference of the iris, from which numerous converging branches run, in the substance of the iris, to its pupillary margin, where they form a second arterial circle, the circulus arteriosus minor. The anterior ciliary arteries are derived from the muscular branches; they run to the front of the eyeball in company with the tendons of the Recti, form a vascular zone beneath the conjunctiva, and then pierce the sclera a short distance from the cornea and end in the circulus ar-teriosus major.

The Muscular Branches, (rami musculares), two in number, superior and inferior, frequently spring from a com-mon trunk. The superior, often wanting, supplies the Levator palpebrae superioris, Rectus superior, and Obliquus superior. The inferior, more constantly present, passes forward between the optic nerve and Rectus inferior, and is distributed to the Recti lateralis, medialis, and inferior, and the Obliquus inferior. This vessel gives off most of the anterior ciliary arteries. Additional muscular branches are given off from the lacrimal and supraorbital arteries, or from the trunk of the ophthalmic.

8. The anterior cerebral artery (a. cerebri anterior) arises from the internal carotid, at the medial extremity of the lateral cerebral fissure. It passes forward and medialward across the anterior perforated substance, above the optic nerve, to the commencement of the longitudinal fissure. Here it comes into close relationship with the opposite artery, to which it is connected by a short trunk, the anterior communicating artery. From this point the two vessels run side by side in the longitudinal fissure, curve around the genu of the corpus callosum, and turning backward continue along the upper surface of the corpus callosum to its posterior part, where they end by anastomosing with the posterior cerebral arteries.

Branches.—In its course the anterior cerebral artery gives off the following branches: Antero-medial Ganglionic, Anterior, Posterior, Inferior, Middle.

The Antero-medial Ganglionic Branches are a group of small arteries which arise at the commencement of the an-terior cerebral artery; they pierce the anterior perforated substance and lamina terminalis, and supply the rostrum of the cor-pus callosum, the septum pellucidum, and the head of the caudate nucleus. The inferior branches, two or three in number, are distributed to the orbital surface of the frontal lobe, where they supply the olfactory lobe, gyrus rectus, and internal or-bital gyrus. The anterior branches supply a part of the superior frontal gyrus, and send twigs over the edge of the hemi-sphere to the superior and middle frontal gyri and upper part of the anterior central gyrus. The middle branches supply the corpus callosum, the cingulate gyrus, the medial surface of the superior frontal gyrus, and the upper part of the anterior cen-tral gyrus. The posterior branches supply the precuneus and adjacent lateral surface of the hemisphere.

The Anterior Communicating Artery (a. communicans anterior) connects the two anterior cerebral arteries across the commencement of the longitudinal fissure. Sometimes this vessel is wanting, the two arteries joining together to form a single trunk, which afterward divides; or it may be wholly, or partially, divided into two. Its length averages about 4 mm., but varies greatly. It gives off some of the antero-medial ganglionic vessels, but these are principally derived from the ante-rior cerebral.

9. The middle cerebral artery (a. cerebri media), the largest branch of the internal carotid, runs at first lateralward in the lateral cerebral or Sylvian fissure and then backward and upward on the surface of the insula, where it divides into a number of branches which are distributed to the lateral surface of the cerebral hemisphere

Branches.—The branches of this vessel are the: Antero-lateral Ganglionic, Inferior Lateral Frontal, Ascending Pari-etal, Parietotemporal, Ascending Frontal, Temporal.

The Antero-lateral Ganglionic Branches, a group of small arteries which arise at the commencement of the middle cerebral artery, are arranged in two sets: one, the internal striate, passes upward through the inner segments of the lentiform nucleus, and supplies it, the caudate nucleus, and the internal capsule; the other, the external striate, ascends through the outer segment of the lentiform nucleus, and supplies the caudate nucleus and the thalamus. One artery of this group is of larger size than the rest, and is of special importance, as being the artery in the brain most frequently ruptured; it has been termed by Charcot the artery of cerebral hemorrhage. It ascends between the lentiform nucleus and the external capsule, and ends in the caudate nucleus. The inferior lateral frontal supplies the inferior frontal gyrus (Broca’s convolu-tion) and the lateral part of the orbital surface of the frontal lobe. The ascending frontal supplies the anterior central gyrus. The ascending parietal is distributed to the posterior central gyrus and the lower part of the superior parietal lobule. The parietotemporal supplies the supramarginal and angular gyri, and the posterior parts of the superior and middle temporal gyri. The temporal branches, two or three in number, are distributed to the lateral surface of the temporal lobe.

10. The posterior communicating artery (a. communicans posterior) runs backward from the internal carotid, and anastomoses with the posterior cerebral, a branch of the basilar. It varies in size, being sometimes small, and occasionally so large that the posterior cerebral may be considered as arising from the internal carotid rather than from the basilar. It is frequently larger on one side than on the other. From its posterior half are given off a number of small branches, the pos-tero-medial ganglionic branches, which, with similar vessels from the posterior cerebral, pierce the posterior perforated substance and supply the medial surface of the thalami and the walls of the third ventricle.

11. The anterior choroidal (a. chorioidea; choroid artery) is a small but constant branch, which arises from the in-ternal carotid, near the posterior communicating artery. Passing backward and lateralward between the temporal lobe and the cerebral peduncle, it enters the inferior horn of the lateral ventricle through the choroidal fissure and ends in the choroid plexus. It is distributed to the hippocampus, fimbria, tela chorioidea of the third ventricle, and choroid plexus.

Practice skillsStudents are supposed to identify the following structures on the samples:

Internal carotid artery- cervical part- petrous part- cavernous part

- cerebral part- ophthalmic artery- anterior cerebral artery- posterior communicating artery

Practice class 14. The innervation and blood supplement of the orbital organs.

The aim: to learn the nerve and blood supply of the orbit and orbital organs.Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-

sents special interest for therapists, ophthalmologists and others.The plan of the practice class:

A. Checking of the home assignment: oral quiz or written test control – 30 minutes.B. Summary lecture on the topic by teacher – 30 minutes.

a) Nerve and blood supply of the walls of orbit.b) Nerve and blood supply of the eyeball.c) Nerves and vessels of the retina.d) Nerve and blood supply of the eyelids.e) Nerve and blood supply of the muscles of the eye.f) Nerve and blood supply of the lacrimal gland.

C. Students’ self-taught time – 55 minutesD. Home-task – 5 minutes

For more information see practice classes 8 (Review of cranial nerves. I, II, ІІІ, ІV, VI, ХІ, ХІІ pairs of cranial nerves), 9 (V pair of cranial nerves: the trigeminal nerve), 13 (The internal carotid artery) and self-taught classes 9 (Parasympathetic supplement of the head and neck), 10 (Sympathetic supplement of the head and neck).

Practice class 15. The external carotid arteries: relations, anastomoses, branches, supple-ment. The innervation and blood supplement of the nasal cavity.

The aim: to learn the topography, branches and areas of blood supply of the external carotid artery; to learn nerve and blood supply of the nasal cavity.

Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-sents special interest for therapists.

The plan of the practice class:A. Checking of the home assignment: oral quiz or written test control – 30 minutes.B. Summary lecture on the topic by teacher – 30 minutes.

a) The external carotid artery, its topography, branches and area of blood supply.b) The anastomoses in the external carotid artery system.c) The anastomoses between the systems of external carotid and subclavian arteries.d) The anastomoses between the systems of external and internal carotid arteries.e) Nerve and blood supply of the nasal cavity.

C. Students’ self-taught time – 55 minutesD. Home-task – 5 minutes

The External Carotid Artery (A. Carotis Externa)The external carotid artery begins opposite the upper border of the thyroid cartilage, and, taking a slightly curved

course, passes upward and forward, and then inclines backward to the space behind the neck of the mandible, where it di -vides into the superficial temporal and internal maxillary arteries. It rapidly diminishes in size in its course up the neck, ow-ing to the number and large size of the branches given off from it. In the child, it is somewhat smaller than the internal carotid; but in the adult, the two vessels are of nearly equal size. At its origin, this artery is more superficial, and placed nearer the middle line than the internal carotid, and is contained within the carotid triangle.

Relations.—The external carotid artery is covered by the skin, superficial fascia, Platysma, deep fascia, and anterior margin of the Sternocleidomastoideus; it is crossed by the hypoglossal nerve, by the lingual, ranine, common facial, and su-perior thyroid veins; and by the Digastricus and Stylohyoideus; higher up it passes deeply into the substance of the parotid gland, where it lies deep to the facial nerve and the junction of the temporal and internal maxillary veins. Medial to it are the hyoid bone, the wall of the pharynx, the superior laryngeal nerve, and a portion of the parotid gland. Lateral to it, in the lower part of its course, is the internal carotid artery. Posterior to it, near its origin, is the superior laryngeal nerve; and higher up, it is separated from the internal carotid by the Styloglossus and Stylopharyngeus, the glossopharyngeal nerve, the pharyngeal branch of the vagus, and part of the parotid gland.

Branches.—The branches of the external carotid artery may be divided into four sets.Anterior - Superior Thyroid, Lingual, External Maxillary.Posterior – Occipital, Posterior Auricular.Ascending – Ascending Pharyngeal.Terminal – Superficial Temporal, Internal Maxillary.1. The superior thyroid artery (a. thyreoidea superior) arises from the external carotid artery just below the level

of the greater cornu of the hyoid bone and ends in the thyroid gland.Relations.—From its origin under the anterior border of the Sternocleidomastoideus it runs upward and forward for

a short distance in the carotid triangle, where it is covered by the skin, Platysma, and fascia; it then arches downward be-neath the Omohyoideus, Sternohyoideus, and Sternothyreoideus. To its medial side are the Constrictor pharyngis inferior and the external branch of the superior laryngeal nerve.

Branches.—It distributes twigs to the adjacent muscles, and numerous branches to the thyroid gland, anastomosing with its fellow of the opposite side, and with the inferior thyroid arteries. The branches to the gland are generally two in number; one, the larger, supplies principally the anterior surface; on the isthmus of the gland it anastomoses with the corre-sponding artery of the opposite side: a second branch descends on the posterior surface of the gland and anastomoses with the inferior thyroid artery.

Besides the arteries distributed to the muscles and to the thyroid gland, the branches of the superior thyroid are: Hy-oid. Superior Laryngeal. Sternocleidomastoid. Cricothyroid.

The Hyoid Branch (ramus hyoideus; infrahyoid branch) is small and runs along the lower border of the hyoid bone beneath the Thyreohyoideus and anastomoses with the vessel of the opposite side.

The Sternocleidomastoid Branch (ramus sternocleidomastoideus; sternomastoid branch) runs downward and lat-eralward across the sheath of the common carotid artery, and supplies the Sternocleidomastoideus and neighboring muscles and integument; it frequently arises as a separate branch from the external carotid.

The Superior Laryngeal Artery (a. laryngea superior), larger than either of the preceding, accompanies the inter-nal laryngeal branch of the superior laryngeal nerve, beneath the Thyreohyoideus; it pierces the hyothyroid membrane, and supplies the muscles, mucous membrane, and glands of the larynx, anastomosing with the branch from the opposite side.

The Cricothyroid Branch (ramus cricothyreoideus) is small and runs transversely across the cricothyroid mem-brane, communicating with the artery of the opposite side.

2. The lingual artery (a. lingualis) arises from the external carotid between the superior thyroid and external maxil-lary; it first runs obliquely upward and medialward to the greater cornu of the hyoid bone; it then curves downward and for-ward, forming a loop which is crossed by the hypoglossal nerve, and passing beneath the Digastricus and Stylohyoideus it runs horizontally forward, beneath the Hyoglossus, and finally, ascending almost perpendicularly to the tongue, turns for-ward on its lower surface as far as the tip, under the name of the profunda linguae.

Relations.—Its first, or oblique, portion is superficial, and is contained within the carotid triangle; it rests upon the Constrictor pharyngis medius, and is covered by the Platysma and the fascia of the neck. Its second, or curved, portion also lies upon the Constrictor pharyngis medius, being covered at first by the tendon of the Digastricus and by the Stylohy-oideus, and afterward by the Hyoglossus. Its third, or horizontal, portion lies between the Hyoglossus and Genioglossus. The fourth, or terminal part, under the name of the profunda linguae (ranine artery) runs along the under surface of the tongue to its tip; here it is superficial, being covered only by the mucous membrane; above it is the Longitudinalis inferior, and on the medial side the Genioglossus. The hypoglossal nerve crosses the first part of the lingual artery, but is separated from the second part by the Hyoglossus.

Branches.—The branches of the lingual artery are: Hyoid. Sublingual. Dorsales linguae. Profunda linguae.The Hyoid Branch (ramus hyoideus; suprahyoid branch) runs along the upper border of the hyoid bone, supplying

the muscles attached to it and anastomosing with its fellow of the opposite side.The Arteriae Dorsales Linguae (rami dorsales linguae) consist usually of two or three small branches which arise

beneath the Hyoglossus; they ascend to the back part of the dorsum of the tongue, and supply the mucous membrane in this situation, the glossopalatine arch, the tonsil, soft palate, and epiglottis; anastomosing with the vessels of the opposite side.

The Sublingual Artery (a. sublingualis) arises at the anterior margin of the Hyoglossus, and runs forward between the Genioglossus and Mylohyoideus to the sublingual gland. It supplies the gland and gives branches to the Mylohyoideus and neighboring muscles, and to the mucous membrane of the mouth and gums. One branch runs behind the alveolar process of the mandible in the substance of the gum to anastomose with a similar artery from the other side; another pierces the Mylohyoideus and anastomoses with the submental branch of the external maxillary artery.

The Arteria Profunda Linguae (ranine artery; deep lingual artery) is the terminal portion of the lingual artery; it pursues a tortuous course and runs along the under surface of the tongue, below the Longitudinalis inferior, and above the mucous membrane; it lies on the lateral side of the Genioglossus, accompanied by the lingual nerve. At the tip of the tongue, it is said to anastomose with the artery of the opposite side, but this is denied by Hyrtl. In the mouth, these vessels are placed one on either side of the frenulum linguae.

3. The external maxillary artery (a. maxillaris externa; facial artery), arises in the carotid triangle a little above the lingual artery and, sheltered by the ramus of the mandible, passes obliquely up beneath the Digastricus and Stylohy-oideus, over which it arches to enter a groove on the posterior surface of the submaxillary gland. It then curves upward over the body of the mandible at the antero-inferior angle of the Masseter; passes forward and upward across the cheek to the angle of the mouth, then ascends along the side of the nose, and ends at the medial commissure of the eye, under the name of the angular artery. This vessel, both in the neck and on the face, is remarkably tortuous: in the former situation, to ac-commodate itself to the movements of the pharynx in deglutition; and in the latter, to the movements of the mandible, lips, and cheeks.

Relations.—In the neck, its origin is superficial, being covered by the integument, Platysma, and fascia; it then passes beneath the Digastricus and Stylohyoideus muscles and part of the submaxillary gland, and frequently beneath the hypoglossal nerve. It lies upon the Constrictores pharyngis medius and superior, the latter of which separates it, at the sum-mit of its arch, from the lower and back part of the tonsil. On the face, where it passes over the body of the mandible, it is comparatively superficial, lying immediately beneath the Platysma. In its course over the face, it is covered by the integu -ment, the fat of the cheek, and, near the angle of the mouth, by the Platysma, Risorius, and Zygomaticus. It rests on the Buccinator and Caninus, and passes either over or under the infraorbital head of the Quadratus labii superioris. The anterior facial vein lies lateral to the artery, and takes a more direct course across the face, where it is separated from the artery by a considerable interval. In the neck it lies superficial to the artery. The branches of the facial nerve cross the artery from be-hind forward.

Branches.—The branches of the artery may be divided into two sets: those given off in the neck (cervical), and those on the face (facial).

Cervical Branches – Ascending Palatine, Tonsillar, Glandular, Submental, Muscular.Facial Branches – Inferior Labial, Superior Labial, Lateral Nasal, Angular, Muscular.The Ascending Palatine Artery (a. palatina ascendens) arises close to the origin of the external maxillary artery

and passes up between the Styloglossus and Stylopharyngeus to the side of the pharynx, along which it is continued be -tween the Constrictor pharyngis superior and the Pterygoideus internus to near the base of the skull. It divides near the Lev -ator veli palatini into two branches: one follows the course of this muscle, and, winding over the upper border of the Con-strictor pharyngis superior, supplies the soft palate and the palatine glands, anastomosing with its fellow of the opposite side and with the descending palatine branch of the internal maxillary artery; the other pierces the Constrictor pharyngis su-perior and supplies the palatine tonsil and auditory tube, anastomosing with the tonsillar and ascending pharyngeal arteries.

The Tonsillar Branch (ramus tonsillaris) ascends between the Pterygoideus internus and Styloglossus, and then along the side of the pharynx, perforating the Constrictor pharyngis superior, to ramify in the substance of the palatine ton-sil and root of the tongue.

The Glandular Branches (rami glandulares; submaxillary branches) consist of three or four large vessels, which supply the submaxillary gland, some being prolonged to the neighboring muscles, lymph glands, and integument.

The Submental Artery (a. submentalis) the largest of the cervical branches, is given off from the facial artery just as that vessel quits the submaxillary gland: it runs forward upon the Mylohyoideus, just below the body of the mandible, and beneath the Digastricus. It supplies the surrounding muscles, and anastomoses with the sublingual artery and with the mylohyoid branch of the inferior alveolar; at the symphysis menti it turns upward over the border of the mandible and di -vides into a superficial and a deep branch. The superficial branch passes between the integument and Quadratus labii inferi-oris, and anastomoses with the inferior labial artery; the deep branch runs between the muscle and the bone, supplies the lip, and anastomoses with the inferior labial and mental arteries.

The Inferior Labial Artery (a. labialis inferior; inferior coronary artery) arises near the angle of the mouth; it passes upward and forward beneath the Triangularis and, penetrating the Orbicularis oris, runs in a tortuous course along the edge of the lower lip between this muscle and the mucous membrane. It supplies the labial glands, the mucous mem -brane, and the muscles of the lower lip; and anastomoses with the artery of the opposite side, and with the mental branch of the inferior alveolar artery.

The Superior Labial Artery (a. labialis superior; superior coronary artery) is larger and more tortuous than the in-ferior. It follows a similar course along the edge of the upper lip, lying between the mucous membrane and the Orbicularis oris, and anastomoses with the artery of the opposite side. It supplies the upper lip, and gives off in its course two or three vessels which ascend to the nose; a septal branch ramifies on the nasal septum as far as the point of the nose, and an alar branch supplies the ala of the nose.

The Lateral Nasal branch is derived from the external maxillary as that vessel ascends along the side of the nose. It supplies the ala and dorsum of the nose, anastomosing with its fellow, with the septal and alar branches, with the dorsal nasal branch of the ophthalmic, and with the infraorbital branch of the internal maxillary.

The Angular Artery (a. angularis) is the terminal part of the external maxillary; it ascends to the medial angle of the orbit, imbedded in the fibers of the angular head of the Quadratus labii superioris, and accompanied by the angular vein. On the cheek it distributes branches which anastomose with the infraorbital; after supplying the lacrimal sac and Orbicu-laris oculi, it ends by anastomosing with the dorsal nasal branch of the ophthalmic artery.

The Muscular Branches in the neck are distributed to the Pterygoideus internus and Stylohyoideus, and on the face to the Masseter and Buccinator. The anastomoses of the external maxillary artery are very numerous, not only with the ves-sel of the opposite side, but, in the neck, with the sublingual branch of the lingual, with the ascending pharyngeal, and by its ascending palatine and tonsillar branches with the palatine branch of the internal maxillary; on the face, with the mental branch of the inferior alveolar as it emerges from the mental foramen, with the transverse facial branch of the superficial temporal, with the infraorbital branch of the internal maxillary, and with the dorsal nasal branch of the ophthalmic.

Peculiarities.—The external maxillary artery not infrequently arises in common with the lingual. It varies in its size and in the extent to which it supplies the face; it occasionally ends as the submental, and not infrequently extends only as high as the angle of the mouth or nose. The deficiency is then compensated for by enlargement of one of the neighboring arteries.

4. The occipital artery (a. occipitalis) arises from the posterior part of the external carotid, opposite the external maxillary, near the lower margin of the posterior belly of the Digastricus, and ends in the posterior part of the scalp.

Course and Relations.—At its origin, it is covered by the posterior belly of the Digastricus and the Stylohyoideus, and the hypoglossal nerve winds around it from behind forward; higher up, it crosses the internal carotid artery, the internal jugular vein, and the vagus and accessory nerves. It next ascends to the interval between the transverse process of the atlas and the mastoid process of the temporal bone, and passes horizontally backward, grooving the surface of the latter bone, being covered by the Sternocleidomastoideus, Splenius capitis, Longissimus capitis, and Digastricus, and resting upon the Rectus capitis lateralis, the Obliquus superior, and Semispinalis capitis. It then changes its course and runs vertically up-ward, pierces the fascia connecting the cranial attachment of the Trapezius with the Sternocleidomastoideus, and ascends in a tortuous course in the superficial fascia of the scalp, where it divides into numerous branches, which reach as high as the vertex of the skull and anastomose with the posterior auricular and superficial temporal arteries. Its terminal portion is ac -companied by the greater occipital nerve.

Branches.—The branches of the occipital artery are: Muscular. Sternocleidomastoid. Auricular. Meningeal. De-scending.

The Muscular Branches (rami musculares) supply the Digastricus, Stylohyoideus, Splenius, and Longissimus capi-tis.

The Sternocleidomastoid Artery (a. sternocleidomastoidea; sternomastoid artery) generally arises from the occip-ital close to its commencement, but sometimes springs directly from the external carotid. It passes downward and backward over the hypoglossal nerve, and enters the substance of the muscle, in company with the accessory nerve.

The Auricular Branch (ramus auricularis) supplies the back of the concha and frequently gives off a branch, which enters the skull through the mastoid foramen and supplies the dura mater, the diploë, and the mastoid cells; this latter branch sometimes arises from the occipital artery, and is then known as the mastoid branch.

The Meningeal Branch (ramus meningeus; dural branch) ascends with the internal jugular vein, and enters the skull through the jugular foramen and condyloid canal, to supply the dura mater in the posterior fossa.

The Descending Branch (ramus descendens; arteria princeps cervicis), the largest branch of the occipital, descends on the back of the neck, and divides into a superficial and deep portion. The superficial portion runs beneath the Splenius,

giving off branches which pierce that muscle to supply the Trapezius and anastomose with the ascending branch of the transverse cervical: the deep portion runs down between the Semispinales capitis and colli, and anastomoses with the verte-bral and with the a. profunda cervicalis, a branch of the costocervical trunk. The anastomosis between these vessels assists in establishing the collateral circulation after ligature of the common carotid or subclavian artery.

The terminal branches of the occipital artery are distributed to the back of the head: they are very tortuous, and lie between the integument and Occipitalis, anastomosing with the artery of the opposite side and with the posterior auricular and temporal arteries, and supplying the Occipitalis, the integument, and pericranium. One of the terminal branches may give off a meningeal twig which passes through the parietal foramen.

5. The posterior auricular artery (a. auricularis posterior) is small and arises from the external carotid, above the Digastricus and Stylohyoideus, opposite the apex of the styloid process. It ascends, under cover of the parotid gland, on the styloid process of the temporal bone, to the groove between the cartilage of the ear and the mastoid process, immediately above which it divides into its auricular and occipital branches.

Branches.—Besides several small branches to the Digastricus, Stylohyoideus, and Sternocleidomastoideus, and to the parotid gland, this vessel gives off three branches: Stylomastoid. Auricular. Occipital.

The Stylomastoid Artery (a. stylomastoidea) enters the stylomastoid foramen and supplies the tympanic cavity, the tympanic antrum and mastoid cells, and the semicircular canals. In the young subject a branch from this vessel forms, with the anterior tympanic artery from the internal maxillary, a vascular circle, which surrounds the tympanic membrane, and from which delicate vessels ramify on that membrane. It anastomoses with the superficial petrosal branch of the middle meningeal artery by a twig which enters the hiatus canalis facialis.

The Auricular Branch (ramus auricularis) ascends behind the ear, beneath the Auricularis posterior, and is distrib-uted to the back of the auricula, upon which it ramifies minutely, some branches curving around the margin of the cartilage, others perforating it, to supply the anterior surface. It anastomoses with the parietal and anterior auricular branches of the superficial temporal.

The Occipital Branch (ramus occipitalis) passes backward, over the Sternocleidomastoideus, to the scalp above and behind the ear. It supplies the Occipitalis and the scalp in this situation and anastomoses with the occipital artery.

6. The ascending pharyngeal artery (a. pharyngea ascendens), the smallest branch of the external carotid, is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and under the Stylopha -ryngeus. It arises from the back part of the external carotid, near the commencement of that vessel, and ascends vertically between the internal carotid and the side of the pharynx, to the under surface of the base of the skull, lying on the Longus capitis.

Branches.—Its branches are: Pharyngeal. Prevertebral. Palatine. Inferior Tympanic. Posterior Meningeal.The Pharyngeal Branches (rami pharyngei) are three or four in number. Two of these descend to supply the Con-

strictores pharyngis medius and inferior and the Stylopharyngeus, ramifying in their substance and in the mucous mem-brane lining them.

The Palatine Branch varies in size, and may take the place of the ascending palatine branch of the facial artery, when that vessel is small. It passes inward upon the Constrictor pharyngis superior, sends ramifications to the soft palate and tonsil, and supplies a branch to the auditory tube.

The Prevertebral Branches are numerous small vessels, which supply the Longi capitis and colli, the sympathetic trunk, the hypoglossal and vagus nerves, and the lymph glands; they anastomose with the ascending cervical artery.

The Inferior Tympanic Artery (a. tympanica inferior) is a small branch which passes through a minute foramen in the petrous portion of the temporal bone, in company with the tympanic branch of the glossopharyngeal nerve, to supply the medial wall of the tympanic cavity and anastomose with the other tympanic arteries.

The Meningeal Branches are several small vessels, which supply the dura mater. One, the posterior meningeal, enters the cranium through the jugular foramen; a second passes through the foramen lacerum; and occasionally a third through the canal for the hypoglossal nerve.

7. The superficial temporal artery (a. temporalis superficialis), the smaller of the two terminal branches of the ex-ternal carotid, appears, from its direction, to be the continuation of that vessel. It begins in the substance of the parotid gland, behind the neck of the mandible, and corsses over the posterior root of the zygomatic process of the temporal bone; about 5 cm. above this process it divides into two branches, a frontal and a parietal.

Relations.—As it crosses the zygomatic process, it is covered by the Auricularis anterior muscle, and by a dense fascia; it is crossed by the temporal and zygomatic branches of the facial nerve and one or two veins, and is accompanied by the auriculotemporal nerve, which lies immediately behind it.

Branches.—Besides some twigs to the parotid gland, to the temporomandibular joint, and to the Masseter muscle, its branches are: Transverse Facial. Anterior Auricular. Middle Temporal. Frontal. Parietal.

The Transverse Facial Artery (a. transversa faciei) is givien off from the superficial temporal before that vessel quits the parotid gland; running forward through the substance of the gland, it passes transversely across the side of the face, between the parotid duct and the lower border of the zygomatic arch, and divides into numerous branches, which sup-ply the parotid gland and duct, the Masseter, and the integument, and anastomose with the external maxillary, masseteric, buccinator, and infraorbital arteries. This vessel rests on the Masseter, and is accompanied by one or two branches of the facial nerve.

The Middle Temporal Artery (a. temporalis media) arises immediately above the zygomatic arch, and, perforating the temporal fascia, gives branches to the Temporalis, anastomosing with the deep temporal branches of the internal maxil -lary. It occasionally gives off a zygomaticoörbital branch, which runs along the upper border of the zygomatic arch, be-tween the two layers of the temporal fascia, to the lateral angle of the orbit. This branch, which may arise directly from the

superficial temporal artery, supplies the Orbicularis oculi, and anastomoses with the lacrimal and palpebral branches of the ophthalmic artery.

The Anterior Auricular Branches (rami auriculares anteriores) are distributed to the anterior portion of the auric-ula, the lobule, and part of the external meatus, anastomosing with the posterior auricular.

The Frontal Branch (ramus frontalis; anterior temporal) runs tortuously upward and forward to the forehead, sup-plying the muscles, integument, and pericranium in this region, and anastomosing with the supraorbital and frontal arteries.

The Parietal Branch (ramus parietalis; posterior temporal) larger than the frontal, curves upward and backward on the side of the head, lying superficial to the temporal fascia, and anastomosing with its fellow of the opposite side, and with the posterior auricular and occipital arteries.

8. The internal maxillary artery (a. maxillaris interna), the larger of the two terminal branches of the external carotid, arises behind the neck of the mandible, and is at first imbedded in the substance of the parotid gland; it passes for-ward between the ramus of the mandible and the sphenomandibular ligament, and then runs, either superficial or deep to the Pterygoideus externus, to the pterygopalatine fossa. It supplies the deep structures of the face, and may be divided into mandibular, pterygoid, and pterygopalatine portions.

The first or mandibular portion passes horizontally forward, between the ramus of the mandible and the spheno-mandibular ligament, where it lies parallel to and a little below the auriculotemporal nerve; it crosses the inferior alveolar nerve, and runs along the lower border of the Pterygoideus externus.

The second or pterygoid portion runs obliquely forward and upward under cover of the ramus of the mandible and insertion of the Temporalis, on the superficial (very frequently on the deep) surface of the Pterygoideus externus; it then passes between the two heads of origin of this muscle and enters the fossa.

The third or pterygopalatine portion lies in the pterygopalatine fossa in relation with the sphenopalatine ganglion.The branches of this vessel may be divided into three groups, corresponding with its three divisions.Branches of the First or Mandibular Portions. Anterior Tympanic. Middle Meningeal. Deep Auricular. Accessory Meningeal. Inferior Alveolar.The Anterior Tympanic Artery (a. tympanica anterior; tympanic artery) passes upward behind the temporo-

mandibular articulation, enters the tympanic cavity through the petrotympanic fissure, and ramifies upon the tympanic membrane, forming a vascular circle around the membrane with the stylomastoid branch of the posterior auricular, and anastomosing with the artery of the pterygoid canal and with the caroticotympanic branch from the internal carotid.

The Deep Auricular Artery (a. auricularis profunda) often arises in common with the preceding. It ascends in the substance of the parotid gland, behind the temporomandibular articulation, pierces the cartilaginous or bony wall of the ex-ternal acoustic meatus, and supplies its cuticular lining and the outer surface of the tympanic membrane. It gives a branch to the temporomandibular joint.

The Middle Meningeal Artery (a. meningea media; medidural artery) is the largest of the arteries which supply the dura mater. It ascends between the sphenomandibular ligament and the Pterygoideus externus, and between the two roots of the auriculotemporal nerve to the foramen spinosum of the sphenoid bone, through which it enters the cranium; it then runs forward in a groove on the great wing of the sphenoid bone, and divides into two branches, anterior and posterior. The anterior branch, the larger, crosses the great wing of the sphenoid, reaches the groove, or canal, in the sphenoidal an-gle of the parietal bone, and then divides into branches which spread out between the dura mater and internal surface of the cranium, some passing upward as far as the vertex, and others backward to the occipital region. The posterior branch curves backward on the squama of the temporal bone, and, reaching the parietal some distance in front of its mastoid angle, divides into branches which supply the posterior part of the dura mater and cranium. The branches of the middle meningeal artery are distributed partly to the dura mater, but chiefly to the bones; they anastomose with the arteries of the opposite side, and with the anterior and posterior meningeal.

The middle meningeal on entering the cranium gives off the following branches: (1) Numerous small vessels supply the semilunar ganglion and the dura mater in this situation. (2) A superficial petrosal branch enters the hiatus of the facial canal, supplies the facial nerve, and anastomoses with the stylomastoid branch of the posterior auricular artery. (3) A supe-rior tympanic artery runs in the canal for the Tensor tympani, and supplies this muscle and the lining membrane of the canal. (4) Orbital branches pass through the superior orbital fissure or through separate canals in the great wing of the sphenoid, to anastomose with the lacrimal or other branches of the ophthalmic artery. (5) Temporal branches pass through foramina in the great wing of the sphenoid, and anastomose in the temporal fossa with the deep temporal arteries.

The Accessory Meningeal Branch (ramus meningeus accessorius; small meningeal or parvidural branch) is some-times derived from the preceding. It enters the skull through the foramen ovale, and supplies the semilunar ganglion and dura mater.

The Inferior Alveolar Artery (a. alveolaris inferior; inferior dental artery) descends with the inferior alveolar nerve to the mandibular foramen on the medial surface of the ramus of the mandible. It runs along the mandibular canal in the substance of the bone, accompanied by the nerve, and opposite the first premolar tooth divides into two branches, in-cisor and mental. The incisor branch is continued forward beneath the incisor teeth as far as the middle line, where it anas-tomoses with the artery of the opposite side; the mental branch escapes with the nerve at the mental foramen, supplies the chin, and anastomoses with the submental and inferior labial arteries. Near its origin the inferior alveolar artery gives off a lingual branch which descends with the lingual nerve and supplies the mucous membrane of the mouth. As the inferior alveolar artery enters the foramen, it gives off a mylohyoid branch which runs in the mylohyoid groove, and ramifies on the under surface of the Mylohyoideus. The inferior alveolar artery and its incisor branch during their course through the substance of the bone give off a few twigs which are lost in the cancellous tissue, and a series of branches which corre -spond in number to the roots of the teeth: these enter the minute apertures at the extremities of the roots, and supply the pulp of the teeth.

Branches of the Second or Pterygoid Portion.Deep Temporal. Masseteric. Pterygoid. Buccinator.The Deep Temporal Branches, two in number, anterior and posterior, ascend between the Temporalis and the

pericranium; they supply the muscle, and anastomose with the middle temporal artery; the anterior communicates with the lacrimal artery by means of small branches which perforate the zygomatic bone and great wing of the sphenoid.

The Pterygoid Branches (rami pterygoidei), irregular in their number and origin, supply the Pterygoidei.The Masseteric Artery (a. masseterica) is small and passes lateralward through the mandibular notch to the deep

surface of the Masseter. It supplies the muscle, and anastomoses with the masseteric branches of the external maxillary and with the transverse facial artery.

The Buccinator Artery (a. buccinatoria; buccal artery) is small and runs obliquely forward, between the Ptery-goideus internus and the insertion of the Temporalis, to the outer surface of the Buccinator, to which it is distributed, anas-tomosing with branches of the external maxillary and with the infraorbital.

Branches of the Third or Pterygopalatine Portion.Posterior Superior Alveolar. Artery of the Pterygoid Canal. Infraorbital. Pharyngeal. Descending Palatine.

Sphenopalatine.The Posterior Superior Alveolar Artery (a. alveolaris superior posterior; alveolar or posterior dental artery) is

given off from the internal maxillary, frequently in conjunction with the infraorbital just as the trunk of the vessel is passing into the pterygopalatine fossa. Descending upon the tuberosity of the maxilla, it divides into numerous branches, some of which enter the alveolar canals, to supply the molar and premolar teeth and the lining of the maxillary sinus, while others are continued forward on the alveolar process to supply the gums.

The Infraorbital Artery (a. infraorbitalis) appears, from its direction, to be the continuation of the trunk of the in-ternal maxillary, but often arises in conjunction with the posterior superior alveolar. It runs along the infraorbital groove and canal with the infraorbital nerve, and emerges on the face through the infraorbital foramen, beneath the infraorbital head of the Quadratus labii superioris. While in the canal, it gives off (a) orbital branches which assist in supplying the Rectus inferior and Obliquus inferior and the lacrimal sac, and (b) anterior superior alveolar branches which descend through the anterior alveolar canals to supply the upper incisor and canine teeth and the mucous membrane of the maxillary sinus. On the face, some branches pass upward to the medial angle of the orbit and the lacrimal sac, anastomosing with the angular branch of the external maxillary artery; others run toward the nose, anastomosing with the dorsal nasal branch of the ophthalmic; and others descend between the Quadratus labii superioris and the Caninus, and anastomose with the exter -nal maxillary, transverse facial, and buccinator arteries. The four remaining branches arise from that portion of the internal maxillary which is contained in the pterygopalatine fossa.

The Descending Palatine Artery (a. palatina descendens) descends through the pterygopalatine canal with the an-terior palatine branch of the sphenopalatine ganglion, and, emerging from the greater palatine foramen, runs forward in a groove on the medial side of the alveolar border of the hard palate to the incisive canal; the terminal branch of the artery passes upward through this canal to anastomose with the sphenopalatine artery. Branches are distributed to the gums, the palatine glands, and the mucous membrane of the roof of the mouth; while in the pterygopalatine canal it gives off twigs which descend in the lesser palatine canals to supply the soft palate and palatine tonsil, anastomosing with the ascending palatine artery.

The Artery of the Pterygoid Canal (a. canalis pterygoidei; Vidian artery) passes backward along the pterygoid canal with the corresponding nerve. It is distributed to the upper part of the pharynx and to the auditory tube, sending into the tympanic cavity a small branch which anastomoses with the other tympanic arteries.

The Pharyngeal Branch is very small; it runs backward through the pharyngeal canal with the pharyngeal nerve, and is distributed to the upper part of the pharynx and to the auditory tube.

The Sphenopalatine Artery (a. sphenopalatina; nasopalatine artery) passes through the sphenopalatine foramen into the cavity of the nose, at the back part of the superior meatus. Here it gives off its posterior lateral nasal branches which spread forward over the conchae and meatuses, anastomose with the ethmoidal arteries and the nasal branches of the descending palatine, and assist in supplying the frontal, maxillary, ethmoidal, and sphenoidal sinuses. Crossing the under surface of the sphenoid the sphenopalatine artery ends on the nasal septum as the posterior septal branches; these anasto-mose with the ethmoidal arteries and the septal branch of the superior labial; one branch descends in a groove on the vomer to the incisive canal and anastomoses with the descending palatine artery.

Practice skillsStudents are supposed to identify the following structures on the samples:

External carotid artery- superior thyroid artery- lingual artery- facial artery- occipital artery- posterior auricular artery

- ascending pharyngeal artery- superficial temporal artery- maxillary artery

- inferior alveolar artery- middle meningeal artery

Practice class 16. The innervation and blood supplement of the organs and cavities of the head and neck. The regional lymphatic nodes and vessels of the neck and head. Examination of self-taught tasks. Tutorial of module 2.

The aim: to learn the nerve and blood supply of the cavities and organs of head and neck; to learn the re-gional lymph nodes and vessels of head and neck.

Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-sents special interest for therapists, surgeons and others.

The plan of the practice class:A. Checking of the home assignment: oral quiz or written test control – 30 minutes.B. Summary lecture on the topic by teacher – 30 minutes.

a) The lymphatics of the head and face.b) The lymphatics of the neck.c) Nerve and vessel supply of the head and neck.

C. Students’ self-taught time – 55 minutesD. Home-task – 5 minutes

The Lymphatics of the Head, Face, and NeckThe Lymph Glands of the Head The lymph glands of the head are arranged in the following groups:Occipital. Facial. Posterior Auricular. Deep Facial. Anterior Auricular. Lingual. Parotid. Retropharyngeal.The occipital glands (lymphoglandulae occipitales), one to three in nu ber, are placed on the back of the head close

to the margin of the Trapezius and resting on the insertion of the Semispinalis capitis. Their afferent vessels drain the oc-cipital region of the scalp, while their efferents pass to the superior deep cervical glands.

The posterior auricular glands (lymphoglandulae auriculares; mastoid glands), usually two in number, are situ-ated on the mastoid insertion of the Sternocleidomastoideus, beneath the Auricularis posterior. Their afferent vessels drain the posterior part of the temporoparietal region, the upper part of the cranial surface of the auricula or pinna, and the back of the external acoustic meatus; their efferents pass to the superior deep cervical glands.

The anterior auricular glands (lymphoglandulae auriculares anteriores; superficial parotid or preauricular glands), from one to three in number, lie immediately in front of the tragus. Their afferents drain the lateral surface of the auricula and the skin of the adjacent part of the temporal region; their efferents pass to the superior deep cervical glands.

The parotid glands (lymphoglandulae parotideae), form two groups in relation with the parotid salivary gland, viz., a group imbedded in the substance of the gland, and a group of subparotid glands lying on the lateral wall of the pharynx. Occasionally small glands are found in the subcutaneous tissue over the parotid gland. Their afferent vessels drain the root of the nose, the eyelids, the frontotemporal region, the external acoustic meatus and the tympanic cavity, possibly also the posterior parts of the palate and the floor of the nasal cavity. The efferents of these glands pass to the superior deep cervical glands. The afferents of the subparotid glands drain the nasal part of the pharynx and the posterior parts of the nasal cavi-ties; their efferents pass to the superior deep cervical glands.

The facial glands comprise three groups: (a) infraorbital or maxillary, scattered over the infraorbital region from the groove between the nose and cheek to the zygomatic arch; (b) buccinator, one or more placed on the Buccinator oppo-site the angle of the mouth; (c) supramandibular, on the outer surface of the mandible, in front of the Masseter and in con-tact with the external maxillary artery and anterior facial vein. Their efferent vessels drain the eyelids, the conjunctiva, and the skin and mucous membrane of the nose and cheek; their efferents pass to the submaxillary glands.

The deep facial glands (lymphoglandulae faciales profunda; internal maxillary glands) are placed beneath the ra-mus of the mandible, on the outer surface of the Pterygoideus externus, in relation to the internal maxillary artery. Their af -ferent vessels drain the temporal and infratemporal fossae and the nasal part of the pharynx their efferents pass to the supe -rior deep cervical glands.

The lingual glands (lymphoglandulae linguales) are two or three small nodules lying on the Hyoglossus and under the Genioglossus. They form merely glandular substations in the course of the lymphatic vessels of the tongue.

The retropharyngeal glands, from one to three in number, lie in the buccopharyngeal fascia, behind the upper part of the pharynx and in front of the arch of the atlas, being separated, however, from the latter by the Longus capitis. Their afferents drain the nasal cavities, the nasal part of the pharynx, and the auditory tubes; their efferents pass to the superior deep cervical glands.

The lymphatic vessels of the scalp are divisible into (a) those of the frontal region, which terminate in the anterior auricular and parotid glands; (b) those of the temporoparietal region, which end in the parotid and posterior auricular glands; and (c) those of the occipital region, which terminate partly in the occipital glands and partly in a trunk which runs down along the posterior border of the Sternocleidomastoideus to end in the inferior deep cervical glands.

The lymphatic vessels of the auricula and external acoustic meatus are also divisible into three groups: (a) an an-terior, from the lateral surface of the auricula and anterior wall of the meatus to the anterior auricular glands; (b) a poste -rior, from the margin of the auricula, the upper part of its cranial surface, the internal surface and posterior wall of the mea-tus to the posterior auricular and superior deep cervical glands; (c) an inferior, from the floor of the meatus and from the lobule of the auricula to the superficial and superior deep cervical glands.

The lymphatic vessels of the face are more numerous than those of the scalp. Those from the eyelids and conjunc-tiva terminate partly in the submaxillary but mainly in the parotid glands. The vessels from the posterior part of the cheek also pass to the parotid glands, while those from the anterior portion of the cheek, the side of the nose, the upper lip, and the lateral portions of the lower lip end in the submaxillary glands. The deeper vessels from the temporal and infratemporal fossae pass to the deep facial and superior deep cervical glands. The deeper vessels of the cheek and lips end, like the su -

perficial, in the submaxillary glands. Both superficial and deep vessels of the central part of the lower lip run to the sub-mental glands.

Lymphatic Vessels of the Nasal Cavities.—Those from the anterior parts of the nasal cavities communicate with the vessels of the integument of the nose and end in the submaxillary glands; those from the posterior two-thirds of the nasal cavities and from the accessory air sinuses pass partly to the retropharyngeal and partly to the superior deep cervical glands.

Lymphatic Vessels of the Mouth.—The vessels of the gums pass to the submaxillary glands; those of the hard palate are continuous in front with those of the upper gum, but pass backward to pierce the Constrictor pharyngis superior and end in the superior deep cervical and subparotid glands; those of the soft palate pass backward and lateralward and end partly in the retropharyngeal and subparotid, and partly in the superior deep cervical glands. The vessels of the anterior part of the floor of the mouth pass either directly to the inferior glands of the superior deep cervical group, or indirectly through the submental glands; from the rest of the floor of the mouth the vessels pass to the submaxillary and superior deep cervical glands.

The lymphatic vessels of the palatine tonsil, usually three to five in number, pierce the buccopharyngeal fascia and constrictor pharyngis superior and pass between the Stylohyoideus and internal jugular vein to the uppermost of the supe -rior deep cervical glands. They end in a gland which lies at the side of the posterior belly of the Digastricus, on the internal jugular vein; occasionally one or two additional vessels run to small glands on the lateral side of the vein under cover of the Sternocleidomastoideus

The lymphatic vessels of the tongue are drained chiefly into the deep cervical glands lying between the posterior belly of the Digastricus and the superior belly of the Omohyoideus; one gland situated at the bifurcation of the common carotid artery is so intimately associated with these vessels that it is known as the principal gland of the tongue. The lym-phatic vessels of the tongue may be divided into four groups: (1) apical, from the tip of the tongue to the suprahyoid glands and principal gland of the tongue; (2) lateral, from the margin of the tongue—some of these pierce the Mylohyoideus to end in the submaxillary glands, others pass down on the Hyoglossus to the superior deep cervical glands; (3) basal, from the region of the vallate papillae to the superior deep cervical glands; and (4) median, a few of which perforate the Mylohy-oideus to reach the submaxillary glands, while the majority turn around the posterior border of the muscle to enter the supe -rior deep cervical glands.

The Lymph Glands of the Neck—The lymph glands of the neck include the following groups:Submaxillary. Superficial Cervical. Submental. Anterior Cervical. Deep Cervical.The submaxillary glands (lymphoglandulae submaxillares), three to six in number, are placed beneath the body of

the mandible in the submaxillary triangle, and rest on the superficial surface of the submaxillary salivary gland. One gland, the middle gland of Stahr, which lies on the external maxillary artery as it turns over the mandible, is the most constant of the series; small lymph glands are sometimes found on the deep surface of the submaxillary salivary glands. The afferents of the submaxillary glands drain the medial palpebral commissure, the cheek, the side of the nose, the upper lip, the lateral part of the lower lip, the gums, and the anterior part of the margin of the tongue; efferent vessels from the facial and sub -mental glands also enter the submaxillary glands. Their efferent vessels pass to the superior deep cervical glands.

The submental or suprahyoid glands are situated between the anterior bellies of the Digastrici. Their afferents drain the central portions of the lower lip and floor of the mouth and the apex of the tongue; their efferents pass partly to the submaxillary glands and partly to a gland of the deep cervical group situated on the internal jugular vein at the level of the cricoid cartilage.

The superficial cervical glands (lymphoglandulae cervicales superficiales) lie in close relationship with the exter-nal jugular vein as it emerges from the parotid gland, and, therefore, superficial to the Sternocleidomastoideus. Their affer-ents drain the lower parts of the auricula and parotid region, while their efferents pass around the anterior margin of the Sternocleidomastoideus to join the superior deep cervical glands.

The anterior cervical glands form an irregular and inconstant group on the front of the larynx and trachea. They may be divided into (a) a superficial set, placed on the anterior jugular vein; (b) a deeper set, which is further subdivided into prelaryngeal, on the middle cricothyroid ligament, and pretracheal, on the front of the trachea. This deeper set drains the lower part of the larynx, the thyroid gland, and the upper part of the trachea; its efferents pass to the lowest of the supe-rior deep cervical glands.

The deep cervical glands (lymphoglandulae cervicales profundae) (Figs. 602, 605) are numerous and of large size: they form a chain along the carotid sheath, lying by the side of the pharynx, esophagus, and trachea, and extending from the base of the skull to the root of the neck. They are usually described in two groups: (1) the superior deep cervical glands lying under the Sternocleidomastoideus in close relation with the accessory nerve and the internal jugular vein, some of the glands lying in front of and others behind the vessel; (2) the inferior deep cervical glands extending beyond the posterior margin of the Sternocleidomastoideus into the supraclavicular triangle, where they are closely related to the brachial plexus and subclavian vein. A few minute paratracheal glands are situated alongside the recurrent nerves on the lateral aspects of the trachea and esophagus. The superior deep cervical glands drain the occipital portion of the scalp, the auricula, the back of the neck, a considerable part of the tongue, the larynx, thyroid gland, trachea, nasal part of the pharynx, nasal cavities, palate, and esophagus. They receive also the efferent vessels from all the other glands of the head and neck, except those from the inferior deep cervical glands. The inferior deep cervical glands drain the back of the scalp and neck, the superficial pectoral region, part of the arm, and, occasionally, part of the superior surface of the liver, In addition, they receive vessels from the superior deep cervical glands. The efferents of the superior deep cervical glands pass partly to the inferior deep cervical glands and partly to a trunk which unites with the efferent vessel of the inferior deep cervical glands and forms the jugular trunk. On the right side, this trunk ends in the junction of the internal jugular and subclavian veins; on the left side it joins the thoracic duct.

Self-taught class 11. The arteries of the orbit, nasal and oral cavity.

The aim: to learn the arteries of the orbit, nasal and oral cavities.Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-

sents special interest for therapists.The plan of the self-taught class:

A. Revise the structures composing the walls of the orbit, nasal and oral cavities, and organs of these cavities.B. Find out the branches of the internal carotid artery supplying the organs of the orbit.C. Find out the anastomoses between the branches of external and internal carotid arteries around the orbit.D. Learn the branches of the external and internal carotid arteries supplying the nasal cavity.E. Learn the branches of the external and internal carotid arteries supplying the oral cavity.F. Learn the branches of the external carotid artery supplying the oral cavity.

For more information see practice classes 13 (The internal carotid arteries: relations, anastomoses, branches), 15 (The external carotid arteries: relations, anastomoses, branches, supplement. The innervation and blood supplement of the nasal cavity), 16 (The innervation and blood supplement of the organs and cavities of the head and neck)

Self-taught class 12. The arteries and veins of the cranial cavity.

The aim: to learn the arteries and veins of the cranial cavity.Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-

sents special interest for therapists.The plan of the self-taught class:

A. Revise the structures composing the anterior, median and posterior cranial fossae.B. Revise the structures which serve for communication of the cranial fossae with other cavities and structures

of the skull.C. Learn the vessel supply of the anterior cranial fossa.D. Learn the vessel supply of the median cranial fossa.E. Learn the vessel supply of the posterior cranial fossa.F. Revise the sinuses of cranial dura mater.G. Learn the blood drainage from the cranial cavity (sinuses of the cranial dura mater, diploic veins, emissary

veins).

The Sinuses of the Dura Mater (Sinus Durae Matris). Ophthalmic Veins and Emissary VeinsThe sinuses of the dura mater are venous channels which drain the blood from the brain; they are devoid of valves,

and are situated between the two layers of the dura mater and lined by endothelium continuous with that which lines the veins. They may be divided into two groups: (1) a postero-superior, at the upper and back part of the skull, and (2) an an-tero-inferior, at the base of the skull.

The postero-superior group comprises theSuperior Sagittal. Inferior Sagittal. Straight. Two Transverse. Occipital.The superior sagittal sinus (sinus sagittalis superior; superior longitudinal sinus) occupies the attached or convex

margin of the falx cerebri. Commencing at the foramen cecum, through which it receives a vein from the nasal cavity, it runs from before backward, grooving the inner surface of the frontal, the adjacent margins of the two parietals, and the su -perior division of the cruciate eminence of the occipital; near the internal occipital protuberance it deviates to one or other side (usually the right), and is continued as the corresponding transverse sinus. It is triangular in section, narrow in front, and gradually increases in size as it passes backward. Its inner surface presents the openings of the superior cerebral veins, which run, for the most part, obliquely forward, and open chiefly at the back part of the sinus, their orifices being concealed by fibrous folds; numerous fibrous bands (chordae Willisii) extend transversely across the inferior angle of the sinus; and, lastly, small openings communicate with irregularly shaped venous spaces (venous lacunae) in the dura mater near the si-nus. There are usually three lacunae on either side of the sinus: a small frontal, a large parietal, and an occipital, intermedi -ate in size between the other two. Most of the cerebral veins from the outer surface of the hemisphere open into these lacu-nae, and numerous arachnoid granulations (Pacchionian bodies) project into them from below. The superior sagittal sinus receives the superior cerebral veins, veins from the diploë and dura mater, and, near the posterior extremity of the sagittal suture, veins from the pericranium, which pass through the parietal foramina.

The numerous communications exist between this sinus and the veins of the nose, scalp, and diploë.The inferior sagittal sinus (sinus sagittalis inferior; inferior longitudinal sinus) is contained in the posterior half or

two-thirds of the free margin of the falx cerebri. It is of a cylindrical form, increases in size as it passes backward, and ends in the straight sinus. It receives several veins from the falx cerebri, and occasionally a few from the medial surfaces of the hemispheres.

The straight sinus (sinus rectus; tentorial sinus) is situated at the line of junction of the falx cerebri with the tento -rium cerebelli. It is triangular in section, increases in size as it proceeds backward, and runs downward and backward from the end of the inferior sagittal sinus to the transverse sinus of the opposite side to that into which the superior sagittal sinus is prolonged. Its terminal part communicates by a cross branch with the confluence of the sinuses. Besides the inferior sagittal sinus, it receives the great cerebral vein (great vein of Galen) and the superior cerebellar veins. A few transverse bands cross its interior.

The transverse sinuses (sinus transversus; lateral sinuses) are of large size and begin at the internal occipital protu-berance; one, generally the right, being the direct continuation of the superior sagittal sinus, the other of the straight sinus. Each transverse sinus passes lateralward and forward, describing a slight curve with its convexity upward, to the base of the petrous portion of the temporal bone, and lies, in this part of its course, in the attached margin of the tentorium cerebelli; it then leaves the tentorium and curves downward and medialward to reach the jugular foramen, where it ends in the internal jugular vein. In its course it rests upon the squama of the occipital, the mastoid angle of the parietal, the mastoid part of the temporal, and, just before its termination, the jugular process of the occipital; the portion which occupies the groove on the mastoid part of the temporal is sometimes termed the sigmoid sinus. The transverse sinuses are frequently of unequal size, that formed by the superior sagittal sinus being the larger; they increase in size as they proceed from behind forward. On transverse section the horizontal portion exhibits a prismatic, the curved portion a semicylindrical form. They receive the blood from the superior petrosal sinuses at the base of the petrous portion of the temporal bone; they communicate with the veins of the pericranium by means of the mastoid and condyloid emissary veins; and they receive some of the inferior cere-bral and inferior cerebellar veins, and some veins from the diploë. The petrosquamous sinus, when present, runs backward along the junction of the squama and petrous portion of the temporal, and opens into the transverse sinus.

The occipital sinus (sinus occipitalis) is the smallest of the cranial sinuses. It is situated in the attached margin of the falx cerebelli, and is generally single, but occasionally there are two. It commences around the margin of the foramen mag-num by several small venous channels, one of which joins the terminal part of the transverse sinus; it communicates with the posterior internal vertebral venous plexuses and ends in the confluence of the sinuses.

The Confluence of the Sinuses (confluens sinuum; torcular Herophili) is the term applied to the dilated extremity of the superior sagittal sinus. It is of irregular form, and is lodged on one side (generally the right) of the internal occipital pro-tuberance. From it the transverse sinus of the same side is derived. It receives also the blood from the occipital sinus, and is connected across the middle line with the commencement of the transverse sinus of the opposite side.

The antero-inferior group of sinuses comprises theTwo Cavernous. Two Intercavernous. Two Superior Petrosal. Two Inferior Petrosal. Basilar Plexus.The cavernous sinuses (sinus cavernosus) are so named because they present a reticulated structure, due to their be-

ing traversed by numerous interlacing filaments. They are of irregular form, larger behind than in front, and are placed one on either side of the body of the sphenoid bone, extending from the superior orbital fissure to the apex of the petrous por -tion of the temporal bone. Each opens behind into the petrosal sinuses. On the medial wall of each sinus is the internal carotid artery, accompanied by filaments of the carotid plexus; near the artery is the abducent nerve; on the lateral wall are the oculomotor and trochlear nerves, and the ophthalmic and maxillary divisions of the trigeminal nerve. These structures are separated from the blood flowing along the sinus by the lining membrane of the sinus. The cavernous sinus receives the superior ophthalmic vein through the superior orbital fissure, some of the cerebral veins, and also the small sphenoparietal sinus, which courses along the under surface of the small wing of the sphenoid. It communicates with the transverse sinus by means of the superior petrosal sinus; with the internal jugular vein through the inferior petrosal sinus and a plexus of veins on the internal carotid artery; with the pterygoid venous plexus through the foramen Vesalii, foramen ovale, and fora -men lacerum, and with the angular vein through the ophthalmic vein. The two sinuses also communicate with each other by means of the anterior and posterior intercavernous sinuses.

The ophthalmic veins, two in number, superior and inferior, are devoid of valves.The Superior Ophthalmic Vein (v. ophthalmica superior) begins at the inner angle of the orbit in a vein named the

nasofrontal which communicates anteriorly with the angular vein; it pursues the same course as the ophthalmic artery, and receives tributaries corresponding to the branches of that vessel. Forming a short single trunk, it passes between the two heads of the Rectus lateralis and through the medial part of the superior orbital fissure, and ends in the cavernous sinus.

The Inferior Ophthalmic Vein (v. ophthalmica inferior) begins in a venous net-work at the forepart of the floor and medial wall of the orbit; it receives some veins from the Rectus inferior, Obliquus inferior, lacrimal sac and eyelids, runs backward in the lower part of the orbit and divides into two branches. One of these passes through the inferior orbital fis -sure and joins the pterygoid venous plexus, while the other enters the cranium through the superior orbital fissure and ends in the cavernous sinus, either by a separate opening, or more frequently in common with the superior ophthalmic vein.

The intercavernous sinuses (sini intercavernosi) are two in number, an anterior and a posterior, and connect the two cavernous sinuses across the middle line. The anterior passes in front of the hypophysis cerebri, the posterior behind it, and they form with the cavernous sinuses a venous circle (circular sinus) around the hypophysis. The anterior one is usually the larger of the two, and one or other is occasionally absent.

The superior petrosal sinus (sinus petrosus superior) small and narrow, connects the cavernous with the transverse sinus. It runs lateralward and backward, from the posterior end of the cavernous sinus, over the trigeminal nerve, and lies in the attached margin of the tentorium cerebelli and in the superior petrosal sulcus of the temporal bone; it joins the trans-verse sinus where the latter curves downward on the inner surface of the mastoid part of the temporal. It receives some cerebellar and inferior cerebral veins, and veins from the tympanic cavity.

The inferior petrosal sinus (sinus petrosus inferior) is situated in the inferior petrosal sulcus formed by the junction of the petrous part of the temporal with the basilar part of the occipital. It begins in the postero-inferior part of the cav -ernous sinus, and, passing through the anterior part of the jugular foramen, ends in the superior bulb of the internal jugular

vein. The inferior petrosal sinus receives the internal auditory veins and also veins from the medulla oblongata, pons, and under surface of the cerebellum.

The exact relation of the parts to one another in the jugular foramen is as follows: the inferior petrosal sinus lies me -dially and anteriorly with the meningeal branch of the ascending pharyngeal artery, and is directed obliquely downward and backward; the transverse sinus is situated at the lateral and back part of the foramen with a meningeal branch of the occipi-tal artery, and between the two sinuses are the glossopharyngeal, vagus, and accessory nerves. These three sets of structures are divided from each other by two processes of fibrous tissue. The junction of the inferior petrosal sinus with the internal jugular vein takes place on the lateral aspect of the nerves.

The basilar plexus (plexus basilaris; transverse or basilar sinus) consists of several interlacing venous channels be-tween the layers of the dura mater over the basilar part of the occipital bone, and serves to connect the two inferior petrosal sinuses. It communicates with the anterior vertebral venous plexus.

Emissary Veins (emissaria).—The emissary veins pass through apertures in the cranial wall and establish commu-nication between the sinuses inside the skull and the veins external to it. Some are always present, others only occasionally so. The principal emissary veins are the following: (1) A mastoid emissary vein, usually present, runs through the mastoid foramen and unites the transverse sinus with the posterior auricular or with the occipital vein. (2) A parietal emissary vein passes through the parietal foramen and connects the superior sagittal sinus with the veins of the scalp. (3) A net-work of minute veins (rete canalis hypoglossi) traverses the hypoglossal canal and joins the transverse sinus with the vertebral vein and deep veins of the neck. (4) An inconstant condyloid emissary vein passes through the condyloid canal and connects the transverse sinus with the deep veins of the neck. (5) A net-work of veins (rete foraminis ovalis) unites the cavernous sinus with the pterygoid plexus through the foramen ovale. (6) Two or three small veins run through the foramen lacerum and connect the cavernous sinus with the pterygoid plexus. (7) The emissary vein of the foramen of Vesalius connects the same parts. (8) An internal carotid plexus of veins traverses the carotid canal and unites the cavernous sinus with the internal jugular vein. (9) A vein is transmitted through the foramen cecum and connects the superior sagittal sinus with the veins of the nasal cavity.

The Diploic Veins (Venae Diploicae)The diploic veins occupy channels in the diploë of the cranial bones. They are large and exhibit at irregular intervals

pouch-like dilatations; their walls are thin, and formed of endothelium resting upon a layer of elastic tissue.So long as the cranial bones are separable from one another, these veins are confined to the particular bones; but

when the sutures are obliterated, they unite with each other, and increase in size. They communicate with the meningeal veins and the sinuses of the dura mater, and with the veins of the pericranium. They consist of (1) the frontal, which opens into the supraorbital vein and the superior sagittal sinus; (2) the anterior temporal, which is confined chiefly to the frontal bone, and opens into the sphenoparietal sinus and into one of the deep temporal veins, through an aperture in the great wing of the sphenoid; (3) the posterior temporal, which is situated in the parietal bone, and ends in the transverse sinus, through an aperture at the mastoid angle of the parietal bone or through the mastoid foramen; and (4) the occipital, the largest of the four, which is confined to the occipital bone, and opens either externally into the occipital vein, or internally into the trans -verse sinus or into the confluence of the sinuses (torcular Herophili).

Practice skillsStudents are supposed to identify the following structures on the samples:

- superior sagittal sinus- inferior sagittal sinus- straight sinus- occipital sinus- transverse sinus

- confluens of sinuses- sigmoid sinus- cavernous sinus- superior petrosal sinus- inferior petrosal sinus

Self-taught class 13. The veins of the head and neck. The veins of the brain.

The aim: to learn the veins of the head and neck; to learn the blood drainage from the brain.Professional orientation: the knowledge of this topic is necessary for doctors of all specialities; it repre-

sents special interest for therapists.The plan of the self-taught class:

A. Learn the tobography and tributarieis of the main veins of head and neck.B. Learn the blood drainage from the brain.

The Veins of the Head and NeckThe veins of the head and neck may be subdivided into three groups: (1) The veins of the exterior of the head and

face. (2) The veins of the neck. (3) The diploic veins, the veins of the brain, and the venous sinuses of the dura mater.The Veins of the Exterior of the Head and Face—The veins of the exterior of the head and face are:Frontal. Superficial Temporal. Supraorbital. Internal Maxillary. Angular. Posterior Facial. Anterior Facial. Posterior

Auricular. Occipital.The frontal vein (v. frontalis) begins on the forehead in a venous plexus which communicates with the frontal

branches of the superficial temporal vein. The veins converge to form a single trunk, which runs downward near the middle line of the forehead parallel with the vein of the opposite side. The two veins are joined, at the root of the nose, by a trans -

verse branch, called the nasal arch, which receives some small veins from the dorsum of the nose. At the root of the nose the veins diverge, and, each at the medial angle of the orbit, joins the supraorbital vein, to form the angular vein. Occa-sionally the frontal veins join to form a single trunk, which bifurcates at the root of the nose into the two angular veins.

The supraorbital vein (v. supraorbitalis) begins on the forehead where it communicates with the frontal branch of the superficial temporal vein. It runs downward superficial to the Frontalis muscle, and joins the frontal vein at the medial angle of the orbit to form the angular vein. Previous to its junction with the frontal vein, it sends through the supraorbital notch into the orbit a branch which communicates with the ophthalmic vein; as this vessel passes through the notch, it re -ceives the frontal diploic vein through a foramen at the bottom of the notch.

The angular vein (v. angularis) formed by the junction of the frontal and supraorbital veins, runs obliquely down-ward, on the side of the root of the nose, to the level of the lower margin of the orbit, where it becomes the anterior facial vein. It receives the veins of the ala nasi, and communicates with the superior ophthalmic vein through the nasofrontal vein, thus establishing an important anastomosis between the anterior facial vein and the cavernous sinus.

The anterior facial vein (v. facialis anterior; facial vein) commences at the side of the root of the nose, and is a di-rect continuation of the angular vein. It lies behind the external maxillary (facial) artery and follows a less tortuous course. It runs obliquely downward and backward, beneath the Zygomaticus and zygomatic head of the Quadratus labii superioris, descends along the anterior border and then on the superficial surface of the Masseter, crosses over the body of the mandible, and passes obliquely backward, beneath the Platysma and cervical fascia, superficial to the submaxillary gland, the Digastricus and Stylohyoideus. It unites with the posterior facial vein to form the common facial vein, which crosses the external carotid artery and enters the internal jugular vein at a variable point below the hyoid bone. From near its termi -nation a communicating branch often runs down the anterior border of the Sternocleidomastoideus to join the lower part of the anterior jugular vein. The facial vein has no valves, and its walls are not so flaccid as most superficial veins.

Tributaries.—The anterior facial vein receives a branch of considerable size, the deep facial vein, from the ptery-goid venous plexus. It is also joined by the superior and inferior palpebral, the superior and inferior labial, the buccinator and the masseteric veins. Below the mandible it receives the submental, palatine, and submaxillary veins, and, generally, the vena comitans of the hypoglossal nerve.

The superficial temporal vein (v. temporalis superficialis) begins on the side and vertex of the skull in a plexus which communicates with the frontal and supraorbital veins, with the corresponding vein of the opposite side, and with the posterior auricular and occipital veins. From this net-work frontal and parietal branches arise, and unite above the zygo-matic arch to form the trunk of the vein, which is joined in this situation by the middle temporal vein, from the substance of the Temporalis. It then crosses the posterior root of the zygomatic arch, enters the substance of the parotid gland, and unites with the internal maxillary vein to form the posterior facial vein.

Tributaries.—The superficial temporal vein receives in its course some parotid veins, articular veins from the tem-poromandibular joint, anterior auricular veins from the auricula, and the transverse facial from the side of the face. The middle temporal vein receives the orbital vein, which is formed by some lateral palpebral branches, and passes backward between the layers of the temporal fascia to join the superficial temporal vein.

The pterygoid plexus (plexus pterygoideus) is of considerable size, and is situated between the Temporalis and Pterygoideus externus, and partly between the two Pterygoidei. It receives tributaries corresponding with the branches of the internal maxillary artery. Thus it receives the sphenopalatine, the middle meningeal, the deep temporal, the pterygoid, masseteric, buccinator, alveolar, and some palatine veins, and a branch which communicates with the ophthalmic vein through the inferior orbital fissure. This plexus communicates freely with the anterior facial vein; it also communicates with the cavernous sinus, by branches through the foramen Vesalii, foramen ovale, and foramen lacerum.

The internal maxillary vein (v. maxillaris interna) is a short trunk which accompanies the first part of the internal maxillary artery. It is formed by a confluence of the veins of the pterygoid plexus, and passes backward between the sphe-nomandibular ligament and the neck of the mandible, and unites with the temporal vein to form the posterior facial vein.

The posterior facial vein (v. facialis posterior; temporomaxillary vein), formed by the union of the superficial tem-poral and internal maxillary veins, descends in the substance of the parotid gland, superficial to the external carotid artery but beneath the facial nerve, between the ramus of the mandible and the Sternocleidomastoideus muscle. It divides into two branches, an anterior, which passes forward and unites with the anterior facial vein to form the common facial vein and a posterior, which is joined by the posterior auricular vein and becomes the external jugular vein.

The posterior auricular vein (v. auricularis posterior) begins upon the side of the head, in a plexus which commu-nicates with the tributaries of the occipital, and superficial temporal veins. It descends behind the auricula, and joins the posterior division of the posterior facial vein to form the external jugular. It receive the stylomastoid vein, and some tribu-taries from the cranial surface of the auricula.

The occipital vein (v. occipitalis) begins in a plexus at the back part of the vertex of the skull, From the plexus emerges a single vessel, which pierces the cranial attachment of the Trapezius and, dipping into the suboccipital triangle, joins the deep cervical and vertebral veins. Occasionally it follows the course of the occipital artery and ends in the internal jugular; in other instances, it joins the posterior auricular and through it opens into the external jugular. The parietal emis-sary vein connects it with the superior sagittal sinus; and as it passes across the mastoid portion of the temporal bone, it re -ceives the mastoid emissary vein which connects it with the transverse sinus. The occipital diploic vein sometimes joins it.

The veins of the neck, which return the blood from the head and face, are:External Jugular. Posterior External Jugular. Anterior Jugular. Internal Jugular. Vertebral.The external jugular vein (v. jugularis externa) receives the greater part of the blood from the exterior of the cra-

nium and the deep parts of the face, being formed by the junction of the posterior division of the posterior facial with the posterior auricular vein. It commences in the substance of the parotid gland, on a level with the angle of the mandible, and runs perpendicularly down the neck, in the direction of a line drawn from the angle of the mandible to the middle of the

clavicle at the posterior border of the Sternocleidomastoideus. In its course it crosses the Sternocleidomastoideus obliquely, and in the subclavian triangle perforates the deep fascia, and ends in the subclavian vein, lateral to or in front of the Scalenus anterior. It is separated from the Sternocleidomastoideus by the investing layer of the deep cervical fascia, and is covered by the Platysma, the superficial fascia, and the integument; it crosses the cutaneous cervical nerve, and its upper half runs parallel with the great auricular nerve. The external jugular vein varies in size, bearing an inverse proportion to the other veins of the neck, it is occasionally double. It is provided with two pairs of valves, the lower pair being placed at its entrance into the subclavian vein, the upper in most cases about 4 cm. above the clavicle. The portion of vein between the two sets of valves is often dilated, and is termed the sinus. These valves do not prevent the regurgitation of the blood, or the passage of injection from below upward.

Tributaries.—This vein receives the occipital occasionally, the posterior external jugular, and, near its termination, the transverse cervical, transverse scapular, and anterior jugular veins; in the substance of the parotid, a large branch of communication from the internal jugular joins it.

The posterior external jugular vein (v. jugularis posterior) begins in the occipital region and returns the blood from the skin and superficial muscles in the upper and back part of the neck, lying between the Splenius and Trapezius. It runs down the back part of the neck, and opens into the external jugular vein just below the middle of its course.

The anterior jugular vein (v. jugularis anterior) begins near the hyoid bone by the confluence of several superfi-cial veins from the submaxillary region. It descends between the median line and the anterior border of the Sternocleido-mastoideus, and, at the lower part of the neck, passes beneath that muscle to open into the termination of the external jugu-lar, or, in some instances, into the subclavian vein. It varies considerably in size, bearing usually an inverse proportion to the external jugular; most frequently there are two anterior jugulars, a right and left; but sometimes only one. Its tributaries are some laryngeal veins, and occasionally a small thyroid vein. Just above the sternum the two anterior jugular veins com-municate by a transverse trunk, the venous jugular arch, which receive tributaries from the inferior thyroid veins; each also communicates with the internal jugular. There are no valves in this vein.

The internal jugular vein (v. jugularis interna) collects the blood from the brain, from the superficial parts of the face, and from the neck. It is directly continuous with the transverse sinus, and begins in the posterior compartment of the jugular foramen, at the base of the skull. At its origin it is somewhat dilated, and this dilatation is called the superior bulb. It runs down the side of the neck in a vertical direction, lying at first lateral to the internal carotid artery, and then lateral to the common carotid, and at the root of the neck unites with the subclavian vein to form the innominate vein; a little above its termination is a second dilatation, the inferior bulb. Above, it lies upon the Rectus capitis lateralis, behind the internal carotid artery and the nerves passing through the jugular foramen; lower down, the vein and artery lie upon the same plane, the glossopharyngeal and hypoglossal nerves passing forward between them; the vagus descends between and behind the vein and the artery in the same sheath, and the accessory runs obliquely backward, superficial or deep to the vein. At the root of the neck the right internal jugular vein is placed at a little distance from the common carotid artery, and crosses the first part of the subclavian artery, while the left internal jugular vein usually overlaps the common carotid artery. The left vein is generally smaller than the right, and each contains a pair of valves, which are placed about 2.5 cm. above the termi-nation of the vessel.

Tributaries.—This vein receives in its course the inferior petrosal sinus, the common facial, lingual, pharyngeal, superior and middle thyroid veins, and sometimes the occipital. The thoracic duct on the left side and the right lymphatic duct on the right side open into the angle of union of the internal jugular and subclavian veins.

The Inferior Petrosal Sinus (sinus petrosus inferior) leaves the skull through the anterior part of the jugular fora-men, and joins the superior bulb of the internal jugular vein.

The Lingual Veins (vv. linguales) begin on the dorsum, sides, and under surface of the tongue, and, passing back-ward along the course of the lingual artery, end in the internal jugular vein. The vena comitans of the hypoglossal nerve (ranine vein), a branch of considerable size, begins below the tip of the tongue, and may join the lingual; generally, how -ever, it passes backward on the Hyoglossus, and joins the common facial.

The Pharyngeal Veins (vv. pharyngeae) begin in the pharyngeal plexus on the outer surface of the pharynx, and, after receiving some posterior meningeal veins and the vein of the pterygoid canal, end in the internal jugular. They occa -sionally open into the facial, lingual, or superior thyroid vein.

The Superior Thyroid Vein (v. thyreoidea superioris) begins in the substance and on the surface of the thyroid gland, by tributaries corresponding with the branches of the superior thyroid artery, and ends in the upper part of the inter -nal jugular vein. It receives the superior laryngeal and cricothyroid veins.

The Middle Thyroid Vein collects the blood from the lower part of the thyroid gland, and after being joined by some veins from the larynx and trachea, ends in the lower part of the internal jugular vein.

The common facial and occipital veins have been described.The vertebral vein (v. vertebralis) is formed in the suboccipital triangle, from numerous small tributaries which

spring from the internal vertebral venous plexuses and issue from the vertebral canal above the posterior arch of the atlas. They unite with small veins from the deep muscles at the upper part of the back of the neck, and form a vessel which enters the foramen in the transverse process of the atlas, and descends, forming a dense plexus around the vertebral artery, in the canal formed by the foramina transversaria of the cervical vertebrae. This plexus ends in a single trunk, which emerges from the foramen transversarium of the sixth cervical vertebra, and opens at the root of the neck into the back part of the in-nominate vein near its origin, its mouth being guarded by a pair of valves. On the right side, it crosses the first part of the subclavian artery.

Tributaries.—The vertebral vein communicates with the transverse sinus by a vein which passes through the condyloid canal, when that canal exists. It receives branches from the occipital vein and from the prevertebral muscles,

from the internal and external vertebral venous plexuses, from the anterior vertebral and the deep cervical veins; close to its termination it is sometimes joined by the first intercostal vein.

The Anterior Vertebral Vein commences in a plexus around the transverse processes of the upper cervical verte-brae, descends in company with the ascending cervical artery between the Scalenus anterior and Longus capitis muscles, and opens into the terminal part of the vertebral vein. The Deep Cervical Vein (v. cervicalis profunda; posterior vertebral or posterior deep cervical vein) accompanies its artery between the Semispinales capitis and colli. It begins in the suboc-cipital region by communicating branches from the occipital vein and by small veins from the deep muscles at the back of the neck. It receives tributaries from the plexuses around the spinous processes of the cervical vertebrae, and terminates in the lower part of the vertebral vein.

The Veins of the BrainThe veins of the brain possess no valves, and their walls, owing to the absence of muscular tissue, are extremely

thin. They pierce the arachnoid membrane and the inner or meningeal layer of the dura mater, and open into the cranial ve-nous sinuses. They may be divided into two sets, cerebral and cerebellar.

The cerebral veins (vv. cerebri) are divisible into external and internal groups according as they drain the outer sur-faces or the inner parts of the hemispheres.

The external veins are the superior, inferior, and middle cerebral.The Superior Cerebral Veins (vv. cerebri superiores), eight to twelve in number, drain the superior, lateral, and

medial surfaces of the hemispheres, and are mainly lodged in the sulci between the gyri, but some run across the gyri. They open into the superior sagittal sinus; the anterior veins runs nearly at right angles to the sinus; the posterior and larger veins are directed obliquely forward and open into the sinus in a direction more or less opposed to the current of the blood con -tained within it.

The Middle Cerebral Vein (v. cerebri media; superficial Sylvian vein) begins on the lateral surface of the hemi-sphere, and, running along the lateral cerebral fissure, ends in the cavernous or the sphenoparietal sinus. It is connected ( a) with the superior sagittal sinus by the great anastomotic vein of Trolard, which opens into one of the superior cerebral veins; (b) with the transverse sinus by the posterior anastomotic vein of Labbé, which courses over the temporal lobe.

The Inferior Cerebral Veins (vv. cerebri inferiores), of small size, drain the under surfaces of the hemispheres. Those on the orbital surface of the frontal lobe join the superior cerebral veins, and through these open into the superior sagittal sinus; those of the temporal lobe anastomose with the middle cerebral and basal veins, and join the cavernous, sphenoparietal, and superior petrosal sinuses.

The basal vein is formed at the anterior perforated substance by the union of (a) a small anterior cerebral vein which accompanies the anterior cerebral artery, (b) the deep middle cerebral vein (deep Sylvian vein), which receives trib-utaries from the insula and neighboring gyri, and runs in the lower part of the lateral cerebral fissure, and (c) the inferior striate veins, which leave the corpus striatum through the anterior perforated substance. The basal vein passes backward around the cerebral peduncle, and ends in the internal cerebral vein (vein of Galen); it receives tributaries from the interpe-duncular fossa, the inferior horn of the lateral ventricle, the hippocampal gyrus, and the mid-brain.

The Internal Cerebral Veins (vv. cerebri internae; veins of Galen; deep cerebral veins) drain the deep parts of the hemisphere and are two in number; each is formed near the interventricular foramen by the union of the terminal and choroid veins. They run backward parallel with one another, between the layers of the tela chorioidea of the third ventricle, and beneath the splenium of the corpus callosum, where they unite to form a short trunk, the great cerebral vein; just be-fore their union each receives the corresponding basal vein.

The terminal vein (v. terminalis; vena corporis striati) commences in the groove between the corpus striatum and thalamus, receives numerous veins from both of these parts, and unites behind the crus fornicis with the choroid vein, to form one of the internal cerebral veins. The choroid vein runs along the whole length of the choroid plexus, and receives veins from the hippocampus, the fornix, and the corpus callosum.

The Great Cerebral Vein (v. cerebri magna [Galeni]; great vein of Galen), formed by the union of the two internal cerebral veins, is a short median trunk which curves backward and upward around the splenium of the corpus callosum and ends in the anterior extremity of the straight sinus.

The cerebellar veins are placed on the surface of the cerebellum, and are disposed in two sets, superior and inferior. The superior cerebellar veins (vv. cerebelli superiores) pass partly forward and medialward, across the superior vermis, to end in the straight sinus and the internal cerebral veins, partly lateralward to the transverse and superior petrosal sinuses. The inferior cerebellar veins (vv. cerebelli inferiores) of large size, end in the transverse, superior petrosal, and occipital sinuses.

Practice skillsStudents are supposed to identify the following structures on the samples:

Internal jugular vein- facial vein- retromandibular vein

External jugular vein

- anterior jugular veinSuperior vena cavaBrachiocephalic vein (right, left)

Practice class 17. Examination of module 3.

Written tests of the vessels of head and neckI. Tests of basic theory1. The aorta

A. becomes the descending aorta at TV4B. enters the abdomen at TV 12C. bifurcates into the common iliac arteries at LV4D. b and cE. *a, b and c

2. A patient with an aneurysm of the aortic arch devel-ops hoarseness. Which of the following muscles on the left is most likely to be paralyzed?A. cricothyroidB. sternothyroidC. *posterior cricoarytenoidD. a and cE. none of the above

3. Which of the following are branches of the basilar artery?A. pontine arteriesB. superior cerebellar arteriesC. anterior inferior cerebellar arteriesD. posterior cerebral arteriesE. *all are branches

4. Infection can spread to and from the cavernous sinus and the facial vein via:A. ophthalmic veinsB. pterygoid plexusC. deep facial veinD. a and bE. *a, b and c

5. Tears in the esophageal mucosa are found as a result of prolonged vomiting. Which of the following ar-teries would NOT likely contribute to bleeding from such a lesion?A. inferior thyroid arteryB. esophageal branches from thoracic aortaC. branches from bronchial arteriesD. branches from the left gastric arteryE. *the hepatic artery

6. Which artery lies on the anterior surface of the ante-rior scalene muscle? A. superior thyroid artery B. *ascending cervical artery C. vertebral. artery D. costocervical trunk E. subclavian A

7. All of the following are branches of the maxillary artery, EXCEPT: A. anterior tympanic A B. middle meningeal A C. buccal A D. *posterior auricular A E. inferior alveolar A

8. A rhabdomyosarcoma (malignant striated muscle tu-mor) involves the whole of the middle scalene mus-cle. What structures will be affected by the tumor?A. dorsal scapular nerveB. long thoracic nerveC. subclavian artery, if tumor extends anteriorlyD. a and cE. *a, b and c

9. The subclavian artery passesA. anterior to the phrenic nerveB. anterior to the scalenus anterior muscle

C. posterior to the lower trunk of the brachial plexus

D. posterior to the scalenus medius muscleE. *posterior to the vagus nerve

10. The ophthalmic artery:A. arises from the internal carotid artery within the

middle cranial fossaB. passes within the arachnoid and dural sheaths of

the optic nerveC. leaves the middle cranial fossa by the optic

canal and is inferior to the optic nerveD. a and b E. *a, b, and c

11. Which venous sinus drains the cavernous sinus di-rectly into the internal jugular vein?A. sigmoid sinus B. straight sinus C. transverse sinusD. *inferior petrosal sinusE. inferior sagittal sinus

12. A thrombus located in the left cavernous sinus im-pinging on all structures related to it would cause:A. difficulty in moving the left eye in any directionB. decreased sensation on the lateral wall of the

nasal cavity C. decreased sensation surrounding the orbitD. a dry eye due to decreased function of the

lacrimal glandE. *a, b, and c

13. The internal jugular vein:A. arises from the sigmoid sinusB. descends in the neck moving posterior to lateral

in relationship to the carotid arteryC. unites with the subclavian vein to form the. bra-

chiocephalic veinD. a and cE. *a, b, and c

14. Before sticking a needle or catheter into the carotid sheath, one should know which of the following re-lationships is TRUE:A. the common carotid artery is lateral B. *the internal jugular vein is lateralC. The sympathetic trunk is centralD. the vagus nerve is anteriorE. all of the above are true

15. The esophagus:A. is innervated by splanchnic nerves from the

sympathetic trunk carrying preganglionic fibersB. *receives its blood supply in part from the infe-

rior thyroid artery and a branch from the left gastric artery

C. its immediate venous drainage is totally into the vena caval system

D. begins at CV4E. all of the above

16. The division of the aorta with the fewest branches is normally the: A. *ascending aorta B. aortic arch C. descending thoracic aorta D. abdominal aorta E. same number of branches in all aortic divisions

listed

17. All of the following arteries are branches of the ex-ternal carotid, EXCEPT: A. lingual A B. *ascending cervical A C. superior thyroid A D. posterior auricular A E. occipital A

18. The following statements about the superior vena cava are true, EXCEPT: A. It begins at the level of the right first costal car-

tilage. B. It receives the right and left brachiocephalic and

the azygos veins. C. It follows the right phrenic nerve. D. *It follows the right vagus nerve. E. It enters the right atrium.

19. Blood from epistaxis (nosebleeds) may come from a branch of the: A. facial A B. maxillary A C. opthalmic A D. B and C but not A E. *A, B and C

20. All of the following are characteristics of the dural venous sinuses, EXCEPT: A. They terminate directly or indirectly in the in-

ternal jugular vein. B. *They lie between the dura and the arachnoid

mater. C. Blood from diploic veins drains into them. D. They connect with valveless veins outside the

cranial cavity. E. They receive venous draining of the brain

21. All the following are branches of the external carotid artery, EXCEPT: A. ascending pharyngeal A. B. superior thyroid A. C. occipital A. D. *vertebral A. E. lingual A.

22. The carotid sheath contains all of the following, EX-CEPT: A. internal carotid A. B. common carotid A. C. *sympathetic trunk D. internal jugular V. E. vagus N.

II. Tests from “Step-1” database (with explanation)1. A 63-year-old man complains of trouble swal-

lowing and hoarseness. On physical exam, he is noted to have ptosis and a constricted pupil on the left, and a diminished gag reflex. Neurolog-ical examination shows decreased pain and temperature sensation on the left side of his face and on the right side of his body. Which of the following vessels is most likely occluded?A. Anterior inferior cerebellar artery (AICA)B. Anterior spinal arteryC. Middle cerebral artery (MCA)D. Posterior cerebral artery (PCA)E. Posterior inferior cerebellar artery (PICA)Explanation:

The correct answer is E. The signs and symp-toms in this patient are consistent with occlusion of the posterior inferior cerebellar artery (PICA). PICA is a branch of the vertebral artery (which is it-self a branch of the subclavian artery). Occlusion of PICA causes a lateral medullary syndrome charac-terized by deficits in pain and temperature sensation over the contralateral body (spinothalamic tract dysfunction); ipsilateral dysphagia, hoarseness, and diminished gag reflex (interruption of the vagal and glossopharyngeal pathways); vertigo, diplopia, nys-tagmus, and vomiting (vestibular dysfunction); ipsi-lateral Horner's syndrome (disruption of descending sympathetic fibers); and ipsilateral loss of pain and temperature sensation of the face (lesion of the spinal tract and nucleus of the trigeminal nerve).

AICA (choice A) is a branch of the basilar artery. Occlusion of this artery produces a lateral in-ferior pontine syndrome, which is characterized by ipsilateral facial paralysis due to a lesion of the fa-cial nucleus, ipsilateral cochlear nucleus damage leading to sensorineural deafness, vestibular in-volvement leading to nystagmus, and spinal trigem-inal involvement leading to ipsilateral pain and tem-perature loss of the face. Also, there is ipsilateral dystaxia due to damage to the middle and inferior cerebellar peduncles.

The anterior spinal artery (choice B) is a branch of the vertebral artery. Occlusion produces the me-dial medullary syndrome, characterized by con-tralateral hemiparesis of the lower extremities and trunk due to corticospinal tract involvement. Medial lemniscus involvement leads to diminished proprio-ception on the contralateral side, and ipsilateral paralysis of the tongue ensues from damage to the hypoglossal nucleus.

The MCA (choice C) is a terminal branch of the internal carotid artery. Occlusion results in con-tralateral face and arm paralysis and sensory loss. Aphasia is produced if the dominant hemisphere is affected, left-sided neglect ensues if the right pari-etal lobe is affected, and quadrantanopsia or homonymous hemianopsia occur when there is damage to the optic radiations.

The PCA (choice D) arises from the terminal bifurcation of the basilar artery. Occlusion results in a homonymous hemianopsia of the contralateral visual field. Often, there is macular sparing.2. A 46-year-old man sustains a spider bite on his

upper eyelid, and an infection develops. The physician is very concerned about spread of the infection to the dural venous sinuses of the brain via emissary veins. With which of the fol-lowing dural venous sinuses does the superior ophthalmic vein directly communicate?A. Cavernous sinusB. Occipital sinusC. Sigmoid sinusD. Superior petrosal sinus

E. Straight sinusExplanation:The correct answer is A. The anterior continua-

tion of the cavernous sinus, the superior ophthalmic vein, passes through the superior orbital fissure to enter the orbit. Veins of the face communicate with the superior ophthalmic vein. Because of the ab-sence of valves in emissary veins, venous flow may occur in either direction. Cutaneous infections may be carried into the cavernous sinus and result in a cavernous sinus infection which may lead to an in-fected cavernous sinus thrombosis. The cavernous sinus is lateral to the pituitary gland and contains portions of cranial nerves III, IV, V1, V2 and VI, and the internal carotid artery.

The occipital sinus (choice B) is at the base of the falx cerebelli in the posterior cranial fossa. It drains into the confluence of sinuses.

The sigmoid sinus (choice C) is the anterior continuation of the transverse sinus in the middle cranial fossa. The sigmoid sinus passes through the jugular foramen and drains into the internal jugular vein.

The superior petrosal sinus (choice D) is at the apex of the petrous portion of the temporal bone and is a posterior continuation of the cavernous si-nus. The superior petrosal sinus connects the cav-ernous sinus with the sigmoid sinus.

The straight sinus (choice E) is at the intersec-tion of the falx cerebri and the falx cerebelli in the posterior cranial fossa. The straight sinus connects the inferior sagittal sinus with the confluence of si-nuses.III. Tests of “Krok-1” database1. A casualty has a trauma of soft tissues and pari-

etal bones in the saggi-tal suture area with pro-fuse bleeding. What formation is probably in-jured?A. Sinus rectus.B. Sinus petrosus superior.C. *Sinus sagittalis superior.D. Sinus sagittalis inferior.E. Sinus transverses.

2. A 37-year-old victim was injured with a sharp object in the interior region of carotid cervical triangle. Which vessel was injured?A. External jugular vein.B. External carotid artery.C. *Common carotid artery.D. Superior thyroid artery.E. Internal carotid artery.

3. A 30-year-old patient was hospitalized due to bleeding of the facial artery. What place on the face has to be pressed to stop bleeding?A. *The mandible’s edge B. The molar bone C. The mental process D. The nose’s back E. The mandible’s branch

4. A victim of a car accident has a contused wound in temporal region. During medical ex-amination a fracture of zygomatic bone and symptoms of intracranial hemorrhage are ob-served. Which artery might be damaged in this region?A. Superficial temporal.B. *Middle meningeal.C. Anterior meningeal.D. Maxillary.E. Facial.

5. An injury of skin in the medial region of the sternocleidomastoid muscle caused air em-bolism. Which cervical vein was damaged?A. Posterior auricular.B. Anterior jugular.C. Internal jugular.D. *External jugular.E. Transverse cervical.

6. After the injury of temporal region a patient got epidural hematoma. Which artery is damaged?A. Deep temporal.B. *Middle meningeal.C. Deep auriculary.D. Superior tympanic.E. Inferior tympanic.

7. A 56-year-old patient has worked for 28 years at a chemical plant in a workshop with harmful production conditions. He often has hemor-rhages of the nasal cavity mucosa. Which arter-ies are involved?A. *Anterior and posterior ethmoid.B. Supraorbital.C. Ciliary.D. Anterior cerebral.E. Ophthalmic.

8. A patient was admitted to a hospital with an open fracture of the ramus of mandible and pro-fuse bleeding in the fracture site. Which artery is damaged?A. A. palatina ascendens.B. A. temporalis media.C. A. facialis.D. A. lingualis.E. *A. alveolaris inferior.

9. A patient has epidural hematoma in the tempo-ral region. Which artery is damaged?A. *Medial meningeal. B. Medial cerebral.C. Posterior communicating.D. Anterior meningeal.E. Anterior cerebral.

10. A patient who got into a car accident has bleed-ing from soft tissues in front of the angle of the mandible. Which vessel must be ligated to stop the bleeding?A. A. lingualis.B. A. carotis interna.C. A. temporalis superficialis.

D. A. alveolaris inferior.E. *A. facialis.

11. A patient has bleeding in the region of the up-per lip. Which artery is damaged?A. A. lingualis.B. A. maxillaris.C. *A. facialis. D. A. temporalis superficialis. E. A. angularis.

12. A patient with a thymus tumor has cyanosis, extension of subcutaneous venous network, edema of soft tissues of the face, neck, upper half of the body, upper limbs. Which venous trunk is blocked?A. *Superior vena cava.

B. External jugular vein.C. Subclavian vein.D. Internal jugular vein.E. Anterior jugular vein.

13. A 50 year-old patient had hemorrhage of the brain and was taken to the hospital. The place of hemorrhage was revealed on the lateral hemispheres surfaces during the medical exami-nation. What artery was injured? A. *The middle cerebral artery B. The posterior cerebral artery C. The anterior cerebral artery D. The posterior communicating artery E. The anterior communicating artery