DENT2062: Block Notes

Amro Farag – Cranial Nerves:

I – Olfactory Nerve:

o Has only sensory function which is for sense of smell

o Consists of olfactory epithelium, bulbs and tracts

o Olfactory epithelium – Damage to this nerve is manifested by anosmia

II – Optic Nerve:

o Sensory function where it conveys visual information from the retina till it

reaches the visual centers of the brain for interpretation

o Damage to this nerve leads to blindness

III – Oculomotor:

o Somatic motor (general somatic effect) supplies four of the six extraocular

muscles of the eye and the levator palpebrae superioris muscle of the upper

eyelid

o Visceral motor (general visceral effect) provides parasympathetic innervation

of the constrictor pupillae and ciliary muscles involved in the pupillary light

and accommodation reflexes

o Damage to the oculomotor can lead to lazy eye, dilated pupil and ptosis

IV – Trochlear:

o Somatic motor (general somatic efferent) innervates the superior oblique

muscle of the contralateral orbit

o Trochlear nerve palsy/Superior oblique dysfunction – Damage produces

vertical diplopia and hypertropia. Most commonly injured cranial nerve in

head trauma

V – Trigeminal:

o 5th cranial nerve, also the largest and most complicated. Different clinical

implications as local anaesthesia, traumatic injuries and viral infections could

affect this nerve.

o Natures of Fibres and Innervations:

Components:

Afferent general Somatic:

o Function :

General sensibility

o Peripheral Distribution:

Sensory branches of the ophthalmic, maxillary

and mandibular nerves to skin, mucous

membranes of the face and head

Efferent Special Visceral:

o Function:

Motor (masticatory function)

o Peripheral Distribution:

Branches to temporalis, masseter, pterygoids,

mylohyoid, tensor timpani and tensor palati

Afferent Proprioceptive:

o Function:

Muscular sensibility

o Peripheral Distribution:

Sensory endings in muscles of mastication

o Branches of the Trigeminal Nerve:

Sensory:

Supplies touch, pain and temperature to the face

Motor:

Supplies muscles of mastication (masseter, temporalis,

pterygoids, mylohyoid and anterior belly of digastric)

These muscles produce elevation, depression, retrusion,

retraction and side-to-side movements of the mandible

The motor division also supplies tensor tympani and tensor

palati

3 branches of the Trigeminal nerve:

Opthalmic

Maxillary

Mandibular

Opthalmic Division:

Purely sensory

Innervates:

o Forehead

o Upper eyelid

o Cornea (corneal reflex), conjunctiva

o Dorsum of nose

Branches into:

o Frontal nerve

o Lacrimal nerve

o Nasociliary nerve

Maxillary Division:

Pure sensory division

Arises from trigeminal ganglion

Leaves cranial cavity through foramen rotundum

Branches of maxillary nerve are:

o Meningeal branch near origin

o Two ganglionic branches arising in the pterygo-palatine

fossa and the sphenopalatine ganglion

o The posterior superior alveolar (dental) nerve and

zygomatic nerve

o The infra-orbital nerve (which is the continuation of the

maxillary nerve)

Innervations of Maxillary Dentition:

o Posterior Superior Alveolar Nerve (With presence of

middle superior alveolar nerve):

Dental pulp

Investing structure

Buccal mucosa upper molars and may give

nerve supply to upper 2nd premolar

o Middle Superior alveolar Nerve:

Upper premolars

Mesiobuccal root of upper 6

Note: Sometimes can be missing and instead

anterior superior and posterior superior alveolar

nerves innervate the premolars instead

o Anterior Superior Alveolar Nerve:

Upper anteriors

Might give supply to upper 1st premolar and if

middle superior alveolar nerve is missing, the

2nd as well

o Palatine Innervations:

Greater palatine - Provides sensation to palatine

mucosa and anastomose with sphenopalatine

fibres in the anterior part of the hard palate

Lesser Palatine - Provides taste nerve fibres,

secretomotor fibres and common sensation to

tissues of the soft palate

Sphenopalatine - Supplies the palatine

supporting structures (palatine mucosa) of the

central and lateral incisors

Mandibular Division:

Largest branch of trigeminal nerve

Mixed sensory/motor fibres

Exits skull through foramen ovale

Carries sensation from:

o Lower lip

o Lower teeth/gums

o Chin/jaw (except angle of mandible which is innervated

by CN2 and CN3)

o Parts of external ear

o Parts of dura of middle cranial fossa

o Mandibular nerve carries touch/position and

pain/temperature sensations from the mouth

Branches:

o Recurrent meningeal nerve

o Medial pterygoid nerve

o Masseteric nerve

o Deep temporal nerve

o Lateral pterygoid nerve

o Buccal nerve

o Auriculotemporal nerve

o Lingual nerve (joined by chorda tympani - branch of

facial nerve)

o Inferior alveolar nerve:

Mylohyoid

Dental

Incisive

Mental

Innervations of lower teeth:

o Inferior Alveolar Nerve:

Supplies pulp and investing structures of

mandibular molars, premolars and anterior teeth

o Lingual Nerve:

Supplies lingual mucoperiosteum of all lower

teeth, anterior 2/3 of the tongue and floor of the

mouth

o Buccal Nerve:

Supplies buccal mucoperiosteum opposite to

lower molars

Accessory Innervations of Mandibular Teeth:

o Lower anterior teeth cross innervate (incisive nerve

crosses midline from one side to another)

o Lower premolars may receive additional nerve supply

from the cutaneous coli nerve (branch from the cervical

plexus of nerves) for their labial mucoperiosteum

o Lower molars may receive additional nerve supply from

the nerve to mylohyoid for the pulp and investing

structures

IV – Abducens:

o Somatic motor – Innervates lateral rectus muscle of ipsilateral orbit

o Damage to the abducens causes issue in left to right movement of the eye

VII – Facial:

o Motor control of most of the muscles of facial expression and posterior belly

of the digastric, the stylohyoid and stapedius of middle ear

o Also receives taste from anterior 2/3 of the tongue via chorda tympani,

VIII – Vestibulocochlear:

o Vestibulocochlear nerve (also called auditory nerve, acoustic nerve or 8th

cranial nerve) consists of two anatomically and functionally distinct parts

which serve equilibrium and hearing

Cochlear nerve is distributed to hearing organ

Vestibular nerve is distributed to organ of equilibrium

o Damage to VIII leads to vertigo and deafness

o Intracranial Branches:

Greater petrosal nerve which provides parasympathetic innervation to

nasal gland, lacrimal gland, palatine gland and pharyngeal gland as

well as the cranial sinuses and nasal cavity

Nerve to stapedius provides motor innervation for stapedius in middle

ear

Chorda tympani innervates submandibular gland, sublingual gland and

taste fibres for the anterior 2/3 of the tongue

o Extracranial Branches:

Posterior auricular controls some movements of scalp muscles around

ear

Branch to posterior belly of the digastric as well as some of the

stylohyoid

Five major facial branches (in parotid gland):

Temporal branch of facial nerve

Zygomatic branch of facial nerve

Buccal branch of facial nerve

Marginal mandibular branch of facial nerve

Cervical branch of facial nerve

IX – Glossopharyngeal:

o Branchial motor (special visceral efferent) – Supplies stylopharyngeus muscle

o Visceral motor (general visceral efferent) – Parasympathetic innervation of the

parotid salivary gland, smooth muscle and glands of the pharynx, larynx and

viscera of the thorax and abdomen

o General visceral afferent – Caries visceral sensory information from the

carotid sinus and body

o General somatic afferent – Provides general sensory information from skin of

external ear, internal surface of the tympanic membrane, upper pharynx and

posterior third of the tongue

o Special sensory (special afferent) – Provides taste sensation from posterior 1/3

of the tongue

X – Vagus Nerve:

o Mixed sensory and motor nerve which wanders into thorax and abdomen and

provides parasympathetic innervation of organs

o Damage to vagus results in dysphagia, hoarseness of voice, loss of cough

reflex (pharynx/larynx), loss of taste sensation in palate (epiglottis)

XI – Accessory Nerve:

o Has cranial root and spinal root both consisting of branchial motor fibres:

Branchial motor cranial root (special visceral efferent) – Innervates

muscles of larynx and pharynx

Branchial motor spinal root (special visceral efferent) – Innervates

trapezius and sternocleidomastoid muscles

XII – Hypoglossal Nerve:

o Has only somatic motor (general somatic efferent) component

o Somatic motor innervates all intrinsic and most of extrinsic tongue muscles

o CN XII supplies three of the four extrinsic muscles of the tongue including

genioglossus, styloglossus and hyoglossus

o Palatoglossus is supplied by CN X (Vagus)

o Runs inferior to the tongue and innervates tongue muscles

o Damage can lead to paralysis of the tongue

Edward Hsu – Arterial Supply of Head and Neck:

Arterial Systems:

o Carotid Artery

Common Carotid Artery Internal Carotid Artery/External Carotid

Artery

o Subclavian Artery

Subclavian Artery:

o Chief arterial supply of upper limb and root of neck contributing branches to

head and brain

o Right artery is a branch of the innominate (branchiocephalic) artery whereas

left is a branch of the arch of the aorta

o Each artery enters neck behind corresponding sternoclavicular joint, curves

upwards for one inch above clavicle (half an inch below apex of the lung) to

end at the outer (lateral) border of the first rib behind the mid clavicular point

where it becomes the axillary artery

o The artery runs behind the scalenus anterior muscle which divides its course

into first, second and third parts

o 3 Parts of the Subclavian Artery as it Relates to the Scalenus Anterior:

Medial part has 3 branches vertebral, thyrocervical trunk and internal

thoracic

Posterior part has 2 branches, costocervical trunk and dorsal scapula

which may also arise from costocervical trunk

Lateral part has no branches

o Branches of the Vertebral Artery:

Grouped as cervical and intra-cranial branches

Cervical Branches:

Spinal branches (into each intervertebral foramen: second

part/segment)

Muscular branches

Intracranial Branches:

Meningeal arteries supply the dura mater of the posterior

cranial fossa

Posterior spinal arteries which descend along the medulla

oblongata

Anterior spinal arteries

Posterior inferior cerebellar artery (perhaps the most tortuous

artery in the body)

o Branches of First Part of the Subclavian Artery:

Thyrocervical Trunk:

Short, wide trunk that arises lateral to vertebral artery and from

upper surface of the subclavian artery and immediately breaks

into 3 branches

Transverse cervical artery

Suprascapular artery

Inferior thyroid artery (largest branch of the trunk)

Internal Thoracic (Mammary) Artery:

Rises from lower surface of the subclavian artery about one

inch above the clavicle. It passes downwards over lung apex

and is crossed by or crosses the phrenic nerve

o Branches of the 2nd and 3rd Parts of the Subclavian Artery:

Branches of the 2nd part of the subclavian are the costocervical

trunk

The 3rd part has no branches

Common Carotid Artery:

o Main arterial supply to the head and neck

o Right artery is a branch of the innominate (brachiocephalic) and the left is a

branch from the aortic arch

o The arteries of the two sides lie deep at the root of the neck where they are

separated by a narrow interval

o Their upper parts are wide apart being separated by the larynx and the pharynx

and become more superficial at the carotid triangles

o Each artery divides at the upper border of the thyroid cartilage (C4) into

external and internal carotid branches at which point there is a dilatation (the

carotid sinus, a baroreceptor). On the posterior aspect of the bifurcation there

is the carotid body (a chemo receptor)

o Each artery lies in its carotid sheath with the internal jugular vein lateral to it

and the vagus nerve between and posterior to them both

Internal Carotid Artery:

o Arises at upper border of thyroid cartilage to enter infratemporal region

o Extends along the side of pharynx until it reaches base of the skull where it

enters carotid canal

o The beginning of the artery shows dilation of the carotid sinus in which walls

are contained (the baroreceptors) which regulate blood pressure (carotid sinus

and carotid body are both supplied by the glossopharyngeal nerve)

o Internal carotid artery is really external (lateral) to the external carotid at its

origin but soon slopes up posteriorly to occupy a medial and deeper level

o No branches in the neck

o Relations of the Petrous Part of the Internal Carotid Artery:

Enters lower opening of the carotid canal in the petrous temporal bone

Within the carotid canal it turns 90o anteromedially to run through the

petrous temporal bone where it lies medial to the middle ear. It then

turns 90o superiorly to pass across upper limit of the foramen lacerum

into the cranial cavity

It the turns 90o anteriorly to pass forwards, lateral to the body of the

sphenoid which it groves. Here it lies in the medial wall of the

cavernous sinus with the abducens nerve (CN VI) on its lateral side

o Relations of the Cavernous Part of the Internal Carotid Artery:

Artery enters cavernous sinus by piercing its posterior wall, it then runs

in its medial wall

At anterior end of cavernous sinus it turns 90o superiorly then 90o

posteriorly to pass medial to anterior clinoid process and lateral to

pituitary stalk and optic chiasma

Pierces roof of cavernous sinus 4mm behind the optic foramen

The ICA ends as terminal branches on the medial surface of the

temporal lobe

Optic nerve runs above and in front of the artery

The oculomotor (CNIII) and trochlear (CNIV) nerves with the

ophthalmic and maxillary divisions of the trigeminal nerve (V1 and

V2) lie in the lateral wall of the sinus

o Relations of the Cerebral Part of the Internal Carotid Artery:

The carotid artery pierces the roof of the cavernous sinus bending

upwards and backwards above it

It lies below the optic nerve but above the oculomotor, finally dividing

into anterior and middle cerebral arteries

o Branches of the Internal Carotid Artery Summary:

Petrous Part:

Caroticotympanic arteries

Pterygoid branch

Cavernous Part:

Hypophyseal branches to the pituitary gland

Meningeal branches

Cerebral Part:

Ophthalmic artery

Posterior communication artery

Anterior choroidal artery

Anterior cerebral artery

Middle cerebral artery

External Carotid Artery:

o Supplies Extracranial structures

o Arises in carotid triangle as terminal branch of common carotid opposite the

upper border of the thyroid cartilage (C4)

o The artery leaves the triangle deep to the digastric muscle, runs upwards and

backwards to enter the submandibular and parotid regions where it ends in the

parotid gland behind the neck of the mandible by dividing into the superficial

temporal and maxillary branches

o It lies at first anteromedially to the internal carotid artery but spirals over it to

the come to lie lateral to it at the level C2

o During its course upwards it is crossed by from below upwards – The upper

root of the ansa cervicalis the hypoglossal nerve, the posterior belly of the

digastric muscle, stylohyoid, muscle, the stylohyoid ligament and facial nerve

within the parotid

o Passing between it and the internal carotid artery are from below and upwards,

the pharyngeal branch of the vagus (CN X), glossopharyngeal

o It lies on, below and upwards, the pharyngeal wall, superior laryngeal branch

of the vagus (CNX) and deep parotid lobe

o Branches:

Mostly arise in carotid triangle at different levels related to tip of the

greater horn of the hyoid bone

Ascending pharyngeal artery

Superior thyroid artery

Lingual artery

Facial artery

Occipital artery

Posterior auricular artery

Maxillary artery

Superficial temporal artery

o Anatomically before the ECA enters the parotid gland, the ECA gives off six

branches, three from in front, one from behind and one deep (medial)

Three in front are superior thyroid, lingual and facial

Two from behind are occipital and posterior auricular

One from medial is ascending pharyngeal

o Ascending Pharyngeal Artery:

Arises from medial side of external carotid, close to its origin, ascends

along the side of pharynx deep to the carotid sheath to reach the base

of the skull. Alongside the ICA (deep) and in front of the prevertebral

fascia

Branches:

Pharyngeal branches

Tonsillar branches

Inferior tympanic branch

Meningeal branches

o Superior Thyroid Artery:

Arises from anterior surface of external carotid (near commencement)

just below tip of greater horn of the hyoid bone, descends almost

vertically downwards with the vein to the upper pole of the thyroid

gland. Close behind it is the external laryngeal nerve

Branches:

Infra-hyoid artery

Superior laryngeal artery

Sterno-mastoid branches to the sterno-mastoid muscle

Crico-thyroid artery runs along the cricothyroid muscle and

membrane anastomosing with the opposite side

o Lingual Artery:

Arises from anterior surface of external carotid artery opposite the tip

of the greater horn of the hyoid bone above the superior thyroid artery

Forms short upward loop, then passes forwards along the upper b order

of the greater horn of the hyoid bone, deep to the hyoglossus muscle

before it enters the submandibular region

Its course is divided into three parts, relative to the hyoglossus muscle

First Part:

Runs in carotid triangle which it leaves by crossing deep to the

digastric muscle to enter the submandibular region

Branches:

o Small, supra-hyoid artery runs along the upper border of

the hyoid bone to anastomose with the opposite side

Second Part:

Runs horizontally under cover of the hyoglossus muscle along

the upper border of the hyoid bone with the lingual vein

Branches:

o 1-2 “dorsalis lingulae arteries” supply the dorsum of the

tongue, the palate and the tonsils

Third Part:

Ascends upwards under anterior border of hyoglossus between

it and the genioglossus towards tip of the tongue where it

becomes the deep artery of the tongue

Branches:

o Deep artery of the tongue (deep lingual artery)

o Sublingual artery which supplies the sublingual salivary

gland and gums anastomosing with the submental artery

o Facial Artery:

Arises in carotid triangle from anterior surface of ECA above the

lingual artery above the tip of the greater horn of the hyoid bone

Leaves carotid region, running upwards on the superior constrictor,

deep to the digastric and stylohyoid muscles to enter the sub-

mandibular region deep to the submandibular salivary gland. It indents

the surface of the gland

Makes S-bend, curling down over submandibular gland and up over

the mandible. Reaching the lower border of the mandible it hooks

around it (its pulsation can be felt 2.5cm in front of the angle of the

mandible at the anterior border of the masseter). It thus enters the face

at the antero-inferior angle of the masseter muscle where it ascends

upwards, forwards and medially towards the angles of the mouth, the

nose and the eye where it ends by anastomosing with the dorsal nasal

branches of the ophthalmic artery

Course of the artery is tortuous so that it can accommodate itself to the

movements of the pharynx during deglutition and the mandible during

opening of the mouth

Can be considered to be of two parts, cervical and facial

Branches of the Cervical Part of the Facial Artery:

Ascending palatine artery

Tonsillar artery

Glandular branches to the sub-mandibular salivary gland

Submental artery (largest branch of the cervical portion)

Branches of the Facial Part of the Facial Artery:

Inferior labial artery – Supplies lower lip anastomosing with

the other side to form the inferior labial arch

Superior labial artery – Supplies the other lip anastomosing

with the other side to form the superior labial arch

The lateral nasal branches – Supplies the ala of the nose

Angular artery – Ends as angular artery which anastomoses

with Infraorbital artery

Muscular branches – Supply adjacent muscle. Posterior belly of

the digastric, stylohyoid, styloglossus, mylohyoid and medial

pterygoid muscle

o Occipital Artery:

Arises from posterior aspect of external carotid artery level with the

facial artery. Ascends upwards and backwards along the lower border

of the posterior belly of the digastric muscle till it reaches the medial

side of the mastoid process crossing the apices of the posterior and

sub-occipital triangles of the neck

Groves the base of the skull at the occipitomastoid suture deep to the

digastric notch on the mastoid process

Finally pierces trapezius muscle to end in posterior part of the scalp

Branches:

Two sternocleidomastoid branches, the upper one accompanies

the accessory nerve to the deep surface the muscle. The lower

branch “holds down” the hypoglossal nerve

Mastoid branch, enters the mastoid foramen to supply the

mastoid air cells

Auricular branches, to the auricle and the muscles of the back

The descending occipital artery

o Posterior Auricular Artery:

Arises from the external carotid artery at the upper border of the

posterior belly of the digastric within the parotid gland under which it

ascends upwards to the back of the auricle till the groove between the

mastoid process and the cartilaginous part of the external acoustic

meatus

It runs superficial to the Styloid process across the upper border of the

digastric

Branches:

Stylomastoid branch

Auricular and occipital branches to the back of the scalp and

the mastoid regions

o Superficial Temporary Artery:

Superficial temporal artery is a terminal branch of the external carotid

arises behind the neck of the mandible within the substance of the

parotid gland

It appears in the temple at the upper pole of the parotid gland where it

crosses the zygomatic arch with its vein in front and the

auriculotemporal nerve behind it

Branches:

Transverse facial artery

Anterior auricular artery

Zygomatico-orbital branch

Middle temporal artery – Largest branch, arises above the

zygomatic arch, pierces temporal fascia and runs deep to the

temporalis muscle supplying it and grooving the bone just

above the external acoustic meatus

Terminal frontal and parietal branches

o Maxillary Artery:

Larger terminal branch, arises in parotid region and ends in pterygo-

palatine fossa where it becomes infra-orbital artery

Arises behind and deep to the neck of the mandible and runs forwards

until it reaches lower border of the lateral pterygoid muscle (first or

mandibular part). It then crosses lower head of the lateral pterygoid

(second or pterygoid part) and finally dips medially between the two

heads of the muscle to enter the pterygo-palatine fossa (third or

pterygo-palatine part)

5 branches from each part. From the first and third parts the five

branches all enter foramina in bones. From the second part none go

through foramina in bones.

First Part (Mandibular) Branches:

Deep auricular artery

Anterior tympanic artery

Middle meningeal artery

Accessory meningeal artery

The inferior alveolar artery is the largest branch of the first part,

descends downwards and forwards behind its own nerve lateral

to the medial pterygoid and the spheno-mandibular ligament, it

enters the mandibular foramen where it divides into incisor and

mental branches

Inferior alveolar and middle meningeal arteries are the most

important, in dissections they arise very near one another and

pass respectively straight down and straight up

Inferior Alveolar Artery:

o Branches:

The mylohyoid artery accompanies mylohyoid

nerve the mylohyoid groove of the mandible. It

anastomoses with the submental branch of facial

artery

The incisor/dental branch arises in mandibular

canal opposite third molar, supplies branches to

the pulps of the teeth and finally anastomoses

with the opposite side

Mental artery leaves the mandible through the

mental foramen to supply the chin region and

anastomose with the inferior labial and

submental branches of the facial artery

Second Part (Pterygoid) Branches:

Deep temporal branches – Supply the deep surface of the

temporalis muscle anastomosing with the middle temporal

artery

Pterygoid branches – Supply pterygoid muscles

The buccal artery – Supplies the buccinators muscle

The masseteric artery – Supplies the masseter muscle

A small artery accompanies the lingual nerve to the tongue

Third Part (Pterygo-Palatine Branches):

The posterior superior alveolar artery enters the back of the

maxilla and supplies branches to the branches of the maxillary

nerve

The greater palatine artery descends through the greater

palatine canal with its nerve to reach the greater palatine

foramen in the hard palate

o It then runs forward in the groove between the palate

and the alveolar part of the maxilla till it reaches the

incisive fossa; there it leaves the fossa through its lateral

foramen to anastomose with branches of the spheno-

palatine artery. 2-3 lesser palatine branches are given to

supply the tonsil and the soft palate

Pharyngeal branches run through a canal to supply the roof of

the nasopharynx and the Eustachian tube

The artery to the pterygoid canal enters the pterygoid canal and

has the same distribution as the pharyngeal branches

The spheno-palatine artery is a long slender branch that leaves

pterygopalate fossa through the spheno-palatine foramen to

enter the posterior part of the nasal cavity where it gives

posterior lateral nasal branches to the superior concha and

meatus of the nose anastomosing for the nasal branches of the

ethmoidal arteries

Infra-Orbital Artery:

Continuation of the maxillary artery, enters the orbit through

the inferior orbital fissure occupying the infra-orbital notch,

groove and canal which carries it to the face where it leaves the

skull through the infraorbital foramen

Throughout its course the artery is accompanied by the

infraorbital nerve and both run in the floor of the orbital cavity

Branches:

o Zygomatic branch, divides into zygomaticofacial and

zygomaticotemporal branches

o Middle superior alveolar artery supplies the sockets of

the premolar teeth and their pulp spaces

o Orbital branches to the contents of the orbit

o Anterior superior alveolar artery supplies the socket and

pulp spaces of the canine and incisors

o Terminal palpebral, nasal and labial

Circle of Willis:

o Anterior cerebral artery (left and right)

o Anterior communicating artery

o Internal carotid artery (left and right)

o Posterior cerebral artery (left and right)

o Posterior communicating artery (left and right)

Alistair Reid – Veins and Lymphatics of the Head and Neck:

Blood Vessels:

o Arteries and veins have same basic structure:

Intima (single layer of endothelium)

Media (muscular) with inner and outer elastic lamina

Adventitia (connective tissue)

o Veins less muscular and elastic

o Veins contain valves

Veins:

o Passively return blood to the heart

o In some instances can actively pulp blood (e.g. deep calf veins and pterygoid

venous plexus via use of muscle pump)

o Controls venous return and therefore cardiac output via nervous and chemical

signalling

Veins of the Head and Neck:

o Internal and External Jugular Systems:

Drain blood from deep and superficial structures

Venous return to the heart

Systems not exclusive to each other (points of communication are

clinically important)

Few valves

Some veins are encased in bone

o External Jugular System:

Formed by union of posterior auricular vein and posterior division of

retromandibular vein behind the angle of the mandible

Runs superficially across the sternocleidomastoid

Runs deep to the platysma and pierces the deep fascia of the neck in

the posterior triangle to enter the subclavian vein

Valves about 4cm about the subclavian

External Jugular Vein:

Drains most of scalp and the face – Superficial temporal vein is

joined by maxillary veins (from pterygoid venous plexus) to

form the retromandibular vein

Just above the clavicle the external jugular vein also receives

the transverse cervical vein, suprascapular vein and anterior

jugular vein

Tributaries:

o Retromandibular vein

Superficial temporal vein

Maxillary veins

o Posterior auricular vein

o Transverse cervical vein

o Suprascapular vein

o Anterior jugular vein

o Internal Jugular Vein:

Begins as continuation of sigmoid sinus as it exits the skull via the

jugular foramen

Drains most of the head and neck

Runs within carotid sheath

Deep to sternocleidomastoid

Marks surface at earlobe to sternoclavicular joint

Tributaries:

Inferior petrosal sinus

Pharyngeal plexus

Facial vein

Lingual vein

Superior thyroid vein

Middle thyroid vein

May receive occipital vein but usually drains to vertebral

plexus

As it exits the skull within the carotid sheath it is initially posterior to

the internal carotid artery and then runs lateral to it

The vagus nerve lies between the internal carotid artery and the

internal jugular vein

The deep cervical nodes are closely adjacent to the internal jugular

vein throughout its course in the neck

Veins are highly variable but the following tributaries usually join at

the level of the hyoid bone (C3)

Pharyngeal plexus

Facial vein

Lingual vein

Distended at superior and inferior ends

o Carotid Sheath:

Connective tissue sheath running from base of skull (at carotid canal)

to aortic arch

Thin over internal jugular vein to allow distension

Contains:

Internal jugular vein

Internal and common carotid arteries

Vagus nerve

Deep cervical nodes

Sympathetic plexus of arteries

Ansa cervicalis

In upper part only contains accessory nerve, hypoglossal nerve

and glossopharyngeal nerve

o Facial Vein:

Supraorbital and suptratrochlear veins pass medial to the medial

canthus of the eyelids to form the angular vein

The angular vein continues as the facial vein

Accompanies the facial artery as it crosses the lower border of the

mandible

Then pierces investing fascia of the neck and is joined by anterior

division of the retromandibular

Tributaries:

Angular vein (supraorbital and suptratrochlear veins)

External nasal vein

Superior labial vein

Inferior labial vein

Anterior branch of retromandibular vein

Submental vein

Sometimes lingual vein and superior thyroid vein

o Lingual Vein:

Joins IJV at level of hyoid

May join IJV directly or have a common trunk with facial vein

Tributaries:

Dorsal lingual vein

Deep lingual vein (from tip of tongue, runs along under surface

of tongue)

Sublingual vein (joins deep lingual vein at anterior border of

hyoglossus to form the venae commitans of the hypoglossal

nerve). Drains either into lingual, facial or internal jugular vein

o Thyroid Veins:

Superior thyroid vein:

Exits upper pole of gland with artery

Drains into IJV or facial vein

Middle thyroid vein:

Short and wide

Drains into IJV

Inferior thyroid vein:

Forms a plexus on pretracheal fascia

Drains into brachiocephalic vein and/or IJV

o Retromandibular Vein:

Tributaries:

Superficial temporal vein

Maxillary veins

Runs down within parotid gland and drains it

Divides into anterior and posterior branches. Posterior branch joins

posterior auricular vein to form the EJV whereas anterior branch joins

facial vein to drain into the IJV

Veins of the Scalp:

o Run with corresponding arteries

o Receive diploic veins from the calvarial bones

Pterygoid Venous Plexus:

o Network of tiny veins within and around lateral pterygoid muscle

o Dilated and easily punctured by needle

o Drains into the paired maxillary veins

Large and short veins

Deep to neck of mandible

Drain into superficial temporal vein

o Aid venous return via pump action of the muscle

Sucks blood from the incompressible parts of head and neck (facial

bones and orbit)

o Tributaries:

Nasopalatine vein

Lateral posterior superior nasal vein

Greater palatine vein

Pharyngeal vein

Infraorbital vein

Inferior ophthalmic vein

Deep facial vein (communicates between plexus and facial vein

anterior to masseter)

Small vein from cavernous sinus via foramen ovale (or foramen of

Vesalius)

o On the posterior aspect of the middle constrictor muscle

o Drains to pterygoid venous plexus or IJV directly

o Communicates with inferior thyroid vein also

o Paratonsillar vein enters Tonsillar bed from soft palate (bleeding post-

tonsillectomy

Ophthalmic Veins:

o Superior ophthalmic vein:

Runs above optic nerve with ophthalmic artery

Communicates with angular vein

o Inferior ophthalmic vein:

Communicates with infraorbital vein and superior ophthalmic vein

Drains to pterygoid venous plexus

Venous Sinuses:

o All lie between inner and outer layers of dura mater (except inferior sagittal

and straight sinuses)

o Drain brain and adjacent skull

o Important communications with veins outside skull

o Cannot collapse

o Valveless

o Include:

Superior sagittal sinus:

Midline between layers of falx cerebri

From foramen caecum to internal occipital protuberance

Usually turns right into lateral (transverse) sinus

Inferior sagittal sinus:

From above crista galli back to free margin of falx cerebri

Flows into straight sinus where falx meets tentorium cerebelli

Straight sinus:

From inferior sagittal IOP

Slopes down at 45o

Turns left to form transverse sinus

Tributaries:

o Inferior sagittal sinus

o Cerebral veins

o Great cerebral vein of Galen

o Veins from occipital lobe and cerebellum

Transverse sinus:

From IOP runs between layers of tentorium cerebelli

Right usually larger

Runs forwards then downwards to become sigmoid sinus.

Superior petrosal sinus ends at this turn

Confluence of sinuses

Sigmoid sinus:

Exits at jugular foramen to become the internal jugular vein

Tributaries:

o Transverse sinus

o Occipital sinus

o Superior petrosal sinus

Occipital sinus

Basilar sinus

Cavernous sinus:

Adjacent to body of sphenoid bone

Middle cranial fossa

Contains internal carotid artery, abducens nerve, oculomotor

nerve, trochlear nerve (ophthalmic and maxillary branches)

Receives blood from orbit, skull and cerebral hemispheres

Tributaries:

o Ophthalmic veins

o Superficial middle cerebral veins

o Sphenoparietal vein

o Superior petrosal sinus

o Inferior petrosal sinus

o Pterygoid venous plexus

Drains Via:

o Superior petrosal sinus

o Inferior petrosal sinus

o Small veins to pterygoid venous plexus

Superior petrosal sinus

Inferior petrosal sinus

Cavernous Sinus Thrombosis:

o Facial infection can produce thrombosis

o Spread of infection via valveless veins

o Painful ophthalmoplegia

o Retrograde thrombosis of inferior petrosal sinus and medullary veins is usually

fatal

Central/Peripheral Venous Communications:

o Facial vein and cavernous sinus – Angular vein communicates with superior

ophthalmic vein

o Deep facial vein and cavernous sinus – Via pterygoid venous plexus

o Posterior auricular vein and sigmoid sinus – Via mastoid emissary vein,

mastoiditis can lead to temporal abscess, meningitis, encephalitis, retrograde

thrombosis and death

Lymph Nodes:

o Lymph transports foreign material to nodes

o Initiation of immune response

o Principally B cells but T cells help

o Innate immune cells also involved

o Enlarge when active

o May be affected by disease:

Reaction to infection

Abscess

Cancer (primary or metastatic)

Granuloma

o Enlarged lymph nodes may:

Indicate presence of infection

Indicate presence of neoplasia

Indicate primary site of either based on knowledge of normal

lymphatic drainage

Lymphatics of Head and Neck:

o No lymphatics in following systems:

Central nervous system

Globe

Inner ear

Cartilage

Bone

Epidermis

o Eventually all lymphs from the head and neck pass through the deep cervical

nodes eventually draining into the thoracic duct (drains whole body except

upper right limb, right thorax, right head and neck), right lymphatic duct and

subclavian vein

o Occipital Nodes:

Apex of posterior triangle

Drains posterior scalp

o Supraclavicular Nodes:

Numerous nodes above clavicle

Outlying deep cervical nodes

o Deep Cervical Nodes:

Lie in loose connective tissue around internal jugular vein

Posterior group pass under sternocleidomastoid to become

supraclavicular group

Parotid drains via upper cervical group

Orbit drains to pre-auricular and then parotid nodes and then to upper

deep cervical nodes

o Submental Nodes:

3-4

Below chin

Drain to submandibular nodes

Drain anterior floor of mouth, lower incisors, lower anterior gingivae,

lower lip and tip of tongue

o Submandibular Nodes:

6 or so

Within and on surface of submandibular gland

Remove gland if treating nodal metastatic disease

Drains submental nodes, lateral of lower lip, external nose, anterior 2/3

of the tongue, anterior nasal walls, paranasal sinus, all other teeth and

submandibular gland

o Retropharyngeal Nodes:

Drain posterior nasal cavity, posterior ethmoidal sinus, sphenoidal

sinus and pharynx

o Jugulodigastric Nodes:

Drain tonsil

Just below angle of mandible

o Tongue Lymphatic Drainage:

Anterior to submental lymph nodes

Lateral to submandibular lymph nodes

Centre to inferior deep cervical lymph nodes

Posterior to deep cervical lymph nodes

Mohammed Mansour – Tissue Spaces of the Face and Neck:

Deep Fascia of the Neck:

o Varies from one region to the other, may be loose layer of connective tissue

when it covers expansible organs such as the buccal cavity or the pharynx or it

may be a firm fibrous membrane as that covering the pre-vertebral muscles

Attachments of the Investing Fascia of the Neck:

o Above – To the external occipital protuberance, the super nuchal line, the

mastoid process and the lower border of the mandible

o Below – To the 7th cervical spine, spine of the scapula, the acromion, the

clavicle and the upper border to the sternum

o Posteriorly – To the nuchal ligament

o Anterior – To the bony prominences of the neck (symphysis menti, hyoid

bone, thyroid and cricoid cartilages and the sternum) and becomes continuous

with the opposite side encasing the infra-hyoid muscles

Investing Fascia of the Neck:

o Between the mastoid process and the angle of the mandible the fascia is split

to enclose the parotid salivary gland blending with and forming its capsule and

covering the masseter muscle to form the parotidomassteric fascia

o At the lower border of the mandible the fascia splits again to enclose the

submandibular salivary gland, its deep lamina ascends to be attached to the

mylohyoid line

o Investing fascia of the neck ensheathes the trapezium lengthwise, behind and

the sternomastoid in front. In between them it forms the roof of the posterior

triangle of the neck

Carotid Sheath:

o Condensation of investing layer of deep fascia, deep to and along the posterior

border of the sternomastoid

o Sheath is well formed over carotid artery but is loosely constructed over

internal jugular vein so as not to interfere with its dilation during times of

increased venous return

o Loosely fixes and supports the vein to the artery

o Attachments:

Above – To base of skull, the tympanic plate and petrous parts of the

temporal bone

Below – Extends behind sternoclavicular joint to the superior

mediastinum of the thorax where it becomes continuous with the

adventitia of the aortic arch

Anterior – Blended to and is continuous with both the pretracheal and

prevertebral fascia which extend between carotid sheaths of both sides

Posterior – Continuous with investing layer of deep fascial and

prevertebral fascia

o Contents:

Above posterior belly of the digastric it contains the ICA

anteromedially, the IJV posterolaterally and CN IX to XII in between

Below the digastric it contains the CCA and the lower part of the ICA

as well as the IJV with the vagus nerve only in between

The limbs of the ansa cervicalis and its loop are embedded on the

anterior wall of the sheath whereas the sympathetic chain is embedded

lengthwise along the posterior wall of the sheath

Pre-Tracheal Fascia:

o Well-formed membrane on which the infra-hyoid muscles can move during

movements of larynx and pharynx

o Attachments:

Above – To hyoid bone and oblique line of thyroid cartilage

Below – Fascia extends behind sternum around the inferior thyroid

veins to blend with fibrous pericardium and adventitia of the aortic

arch

o Split to enclose the thyroid gland, fixing it to the larynx and the 2nd, 3rd and 4th

tracheal rings. Its anterior surface is blended to the fascial sheaths of the infra-

hyoid muscles

Pre-Vertebral Fascia:

o Tough, fibrous membrane that lies in front of the prevertebral muscles forming

a base on which the pharynx, oesophagus and carotid sheaths move during

swallowing

o Attachments:

Medially – Fascia continuous across the median plane with other side

blending with the anterior longitudinal ligament of the vertebral

column

Sideways – Fascia is continuous deep to the carotid sheath and the

sternomastoid muscle with the deep fascia covering the floor of the

posterior triangle

Above – Fascia fixed to base of the skull

Below – Extends to superior mediastinum to be attached to the 3rd

thoracic vertebra

Pharyngeal Fascia:

o Bucco-Pharyngeal Fascia - Covers outer surface of pharyngeal muscles and is

prolonged anteriorly over the buccinator muscle

o Pharyngo-Basilar Fascia – Tough, fibrous membrane that fills gap between the

upper border of the pharynx and base of the skull. Pierced by Eustachian tube

and palatal muscles

o Retro-Pharyngeal Fascia – Forms a loose areolar tissue between posterior wall

of the pharynx, oesophagus and the prevertebral fascia allowing their free

movement

Odontogenic Infections:

o Spread to Primary Spaces:

Sinus

Nasal cavity

Palate

Sublingual

Submandibular

Vestibular

Buccal

o Spread to Secondary Spaces:

Pterygomandibular – Between medial and lateral pterygoid muscles

Masseteric – Spreads from submandibular and buccal

Superficial and deep temporal

Infratemporal space

Lateral pharyngeal space – Migrates from Pterygomandibular space

and contains many vital structures

Retropharyngeal

Prevertebral – “Danger Space 4” between prevertebral and alar

extension

Grodinsky and Holyoke spaces

Amro Farag – Anatomy of the Facial Nerve:

Origin of Facial Nerve:

o Facial nerve nucleus which resides in dors-lateral portion of the pons

o In the cerebellopontine angle the facial nerve is in close proximity to the

nervus intermedius

o Then travels through internal auditory canal

Infratemporal Course (1st Branch):

o 1st branch is the greater superficial petrosal nerve

o Parasympathetic secretory fibres to the nose, mouth and lacrimal gland and

sensory taste fibres from the palate

Infratemporal Course (2nd and 3rd Branches):

o Nerve to stapedius muscle

o Chorda tympani nerve leaves in mastoid bone through petrotympanic fissure

carrying parasympathetic secretory fibres to the submandibular and sublingual

glands and sensory taste fibres from the anterior two-thirds of the tongue

Extratemporal Course:

o Emerges from the stylomastoid foramen

o Mostly divide into upper and lower main branches

o The frontal (temporal) branch and marginal mandibular branches are most

consistent in anatomy

o The other three branches zygomatic, buccal and cervical branches

Muscles:

o Facial nerve innervates a total of 23 paired muscles and the single orbicularis

oris muscle

o Only 18 of the paired muscles act in final expression

o Remaining 5 pairs of muscles move the scalp and ears

o Main muscles of expression:

Frontalis muscle raises the eyebrows

Orbicularis oculi muscle – Closes the eyelids

Zygomaticus major and minor muscles – Instrumental in smiling and

grimacing

Orbicularis oris muscle – Purses the lips

Lower lip depressors – Keep the lip from riding up where it may be

bitten during chewing

Facial Nerve Paralysis:

o Unilateral facial weakness

o Unilateral loss of taste sensation

o Decreased salivation (insignificant)

o Decreased tear secretion (causes eye dryness and corneal ulceration)

Aetiology:

o Idiopathic (Bell’s Palsy)

o Viral infection (Herpes Zoster Virus)

o Trauma (Fractures)

o Tumours (Parotid Salivary Gland Tumours)

Transient Facial Nerve Paralysis:

o Could occur after administrator of inferior alveolar nerve block anaesthesia

o If the needle inserted too deep (not touching bone), injecting the local

anaesthetic solution into the parotid salivary tissue