8-trianglesoftheneck-100517073624-phpapp01

8/13/2019 8-trianglesoftheneck-100517073624-phpapp01

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IMS MSU

Dr. THAAER MOHAMMED DAHER ALSAAD

SPECIALIST IN GENERAL SURGERY

M.B.Ch.B.(MBBS) F.I.B.M.S.(Ph.D.)SENIOR LECTURER


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TRIANGLESOF THENECK


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TRIANGLES OF THE NECK 1/2

Anterolaterally the neck appears as a somewhatquadrilateral area,

limited superiorlyby the base of the mandible and a linecontinued from the angle of the mandible to the mastoid

process, inferiorlyby the upper border of the clavicle,

anteriorlyby the anterior median line,

posteriorlyby the anterior margin of trapezius.

This quadrilateral area can be further divided intoanterior and posterior triangles bysternocleidomastoid, which passes obliquely from thesternum and clavicle to the mastoid process and occipitalbone.


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It is true that these triangles and theirsubdivisions are somewhat arbitrary,

because many major structures-arteries, veins,lymphatics, nerves, and some viscera-transgresstheir boundaries without interruption,nevertheless they have a topographical value indescription.

Moreover, some of their subdivisions are easily

identified by inspection and palpation andprovide invaluable assistance in surfaceanatomical and clinical examination.

TRIANGLES OF THE NECK 2/2


7/80The triangles of the left side of the neck


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Anterior triangle of the neck

is bounded anteriorly by the median line of the neck, posteriorly by the anterior margin of sterno-cleidomastoid.

Its base is the inferior border of the mandible

and its projection to the mastoid process,

and its apex is at the manubrium sterni. It can be subdivided into;

suprahyoid and infrahyoid areas above and below thehyoid bone,

and into digastric, submental, muscular and carotid triangles

by the passage of digastric and omohyoid across theanterior triangle


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Subdivisions of the anterior triangle of the neck-a regional approach


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Dissection of the left anterior

triangle.

Platysma has been dividedtransversely:

its upper part has been turned

upwards on to the face,

and its lower part turned

backwards, exposing the lower

part of sternocleidomastoid.


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DIGASTRIC TRIANGLE 1/2 The digastric triangle is bordered

above by the base of the mandible and its projection to themastoid process,

posteroinferiorly by the posterior belly of digastric and bystylohyoid,

anteroinferiorly by the anterior belly of digastric. It is covered by the skin, superficial fascia, platysma and

deep fascia, which contain branches of the facial andtransverse cutaneous cervical nerves.

Its floor is formed by mylohyoid and hyoglossus.

The anterior region of the digastric triangle contains thesubmandibular gland, which has the facial vein superficialto it and the facial artery deep to it.

The submental and mylohyoid arteries and nerves lie onmylohyoid.


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The submandibular lymph nodes are variably related tothe submandibular gland.

The posterior region of the digastric triangle containsthe lower part of the parotid gland.

The external carotid artery, passing deep to stylohyoid,

curves above the muscle,

and overlaps its superficial surface as it ascends deep to theparotid gland before entering it.

The internal carotid artery, internal jugular vein and vagusnerve lie deeper and are separated from the externalcarotid artery by

styloglossus, stylopharyngeus and the glossopharyngealnerve.

DIGASTRIC TRIANGLE 2/2


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SUBMENTAL TRIANGLE

The single submental triangle is demarcatedby the anterior bellies of both digastricmuscles.

Its apex is at the chin, its base is the body of the hyoid bone

and its floor is formed by both mylohyoid

muscles. It contains lymph nodes and small veins that

unite to form the anterior jugular vein.


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MUSCULAR TRIANGLE

The muscular triangle is bounded,

anteriorly by the median line of the neck fromthe hyoid bone to the sternum,

inferoposteriorly by the anterior margin ofsternocleidomastoid,

posterosuperiorly by the superior belly of

omohyoid. The triangle contains omohyoid, sternohyoid,

sternothyroid and thyrohyoid


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CAROTID TRIANGLE 1/4

The carotid triangle is limited,

posteriorly by sternocleidomastoid,

anteroinferiorly by the superior belly of omohyoid,

and superiorly by stylohyoid and the posterior belly ofdigastric.

In the living (except the obese) the triangle is usually asmall visible triangular depression, sometimes best seen

with the head and cervical vertebral column slightlyextended and the head contralaterally rotated.

The carotid triangle is covered by the skin, superficialfascia, platysma and deep fascia containing branches

of the facial and cutaneous cervical nerves.


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The hyoid bone forms its anterior angle and adjacent

floor and can be located on simple inspection,verified by palpation.

Parts of thyrohyoid, hyoglossus and inferior andmiddle pharyngeal constrictor muscles form its floor.

The carotid triangle contains the upper part of thecommon carotid artery and its division into externaland internal carotid arteries.

Overlapped by the anterior margin ofsternocleidomastoid, the external carotid artery is

first anteromedial, then anterior to the internal carotidartery.

Branches of the external carotid artery areencountered in the carotid triangle.



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. Thus the superior thyroid artery runsanteroinferiorly,

the lingual artery anteriorly with a characteristicupward loop,

the facial artery anterosuperiorly, the occipital artery posterosuperiorly

and the ascending pharyngeal artery medialto the internal carotid artery.Arterial pulsation

greets the examining finger. The superior thyroid, lingual, facial, ascending

pharyngeal and sometimes the occipital, veins,correspond to the branches of the external carotid

artery, and all drain into the internal jugular vein.



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The hypoglossal nerve crosses the external and internal carotid arteries.

It curves round the origin of the lower sternocleidomastoidbranch of the occipital artery,

and at this point the superior root of the ansa cervicalisleaves it to descend anteriorly in the carotid sheath.

The internal laryngeal nerve and, below it, the externallaryngeal nerve, lie medial to the external carotid arterybelow the hyoid bone.

Many structures in this region, such as all or part of theinternal jugular vein, associated deep cervical lymph nodes,and the vagus nerve, may be variably obscured bysternocleidomastoid, and, pedantically, are thus 'outsidethe triangle.



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Posterior triangle of the neck 1/2

The posterior triangle is delimited;

anteriorly by sternocleidomastoid,

posteriorly by the anterior edge of trapezius,

and inferiorly by the middle third of the clavicle.

Its apex is between the attachments ofsternocleidomastoid and trapezius to the occiput and isoften blunted, so that the 'triangle' becomes quadrilateral.

The roof of the posterior triangle is formed by theinvesting layer of the deep cervical fascia.

The floor of the triangle is formed by the prevertebralfascia overlying splenius capitis, levator scapulae and thescalene muscles.


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It is crossed, 2.5 cm above the clavicle, by theinferior belly of omohyoid, which subdivides

it into occipital and supraclavicular triangles.

Collectively these contain the cervical andbrachial plexuses, the subclavian artery andthe spinal accessory nerve.

The muscles forming the floor of the posteriortriangle constitute the anterior and lateralgroups of the prevertebral musculature .

Posterior triangle of the neck 2/2


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OCCIPITAL TRIANGLE 1/2

The occipital triangle constitutes the upper and largerpart of the posterior triangle,

with which it shares the same borders, except thatinferiorly it is limited by the inferior belly of omohyoid.

Its floor is constituted, from above down, by spleniuscapitis, levator scapulae, and scaleni medius andposterior, and semispinalis capitis occasionally appears atthe apex.

It is covered by the skin, superficial and deep fasciae and

below by platysma. The spinal accessory nerve pierces

sternocleidomastoid and crosses levator scapulae obliquelydownwards and backwards to reach the deep surface oftrapezius


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Cutaneous and muscular branches of thecervical plexus emerge at the posteriorborder of sternocleidomastoid.

Inferiorly, supraclavicular nerves, transversecervical vessels and the uppermost part ofthe brachial plexus cross the triangle.

Lymph nodes lie along the posterior border ofsternocleidomastoid from the mastoid processto the root of the neck

OCCIPITAL TRIANGLE 2/2


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SUPRACLAVICULAR TRIANGLE 1/3 The supraclavicular triangle

is the lower and smaller division of the posterior triangle,with which it shares the same boundaries, except thatsuperiorly it is limited by omohyoid.

It corresponds in the living neck with the lower part of a deep,

prominent hollow, namely, the greater supraclavicular fossa. Its floor contains the first rib, scalenus medius and the first

slip of serratus anterior.

Its size varies with the extent of the clavicular attachmentsof sternocleidomastoid and trapezius and also the level of

the inferior belly of omohyoid. The triangle is covered by the skin, superficial and deep

fasciae and platysma and crossed by the supraclavicularnerves.


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Just above the clavicle,

the third part of the subclavian artery curves inferolaterallyfrom the lateral margin of scalenus anterior across the firstrib to the axilla.

The subclavian vein is behind the clavicle and is not usuallyin the triangle; but it may rise as high as the artery andeven accompany it behind scalenus anterior.

The brachial plexus is partly superior, and partly posterior tothe artery and is always closely related to it.

The trunks of the brachial plexus may easily be palpatedhere if the neck is contralaterally flexed and the examiningfinger is drawn across the trunks at right angles to theirlength.

SUPRACLAVICULAR TRIANGLE 2/3


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With the musculature relaxed, pulsation of the subclavianartery may be felt and the arterial flow can be controlled byretroclavicular compression against the first rib.

The suprascapular vessels pass transversely behind theclavicle, below the transverse cervical artery and vein.

The external jugular vein descends behind the posterior border of sternocleidomastoid to end

in the subclavian vein.

It receives the transverse cervical and suprascapular veins, whichform a plexus in front of the third part of the subclavian artery;

occasionally it is joined by a small vein crossing the clavicle anteriorlyfrom the cephalic vein.

The nerve to subclavius crosses the triangle.

The triangle contains some lymph nodes.

SUPRACLAVICULAR TRIANGLE 3/3


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MUSCLES


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PLATYSMA 1/3

Platysma is a broad sheet of muscle of varying prominence.

arises from the fascia covering the upper parts of pectoralismajor and deltoid.

Its fibres cross the clavicle and ascend medially in the sideof the neck.

Anterior fibres interlace across the midline with the fibresof the contralateral muscle, below and behind thesymphysis menti.

Other fibres attach to the lower border of the mandible orto the lower lip or cross the mandible to attach to skin andsubcutaneous tissue of the lower face.


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Vascular supply

Platysma receives its blood supply from

the submental branch of the facial artery

and the suprascapular artery from the thyrocervicaltrunk of the subclavian artery.

Innervation

Platysma is innervated by the cervical branch of

the facial nerve which descends on the deepsurface of the muscle close to the angle of themandible

PLATYSMA 2/3


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Contraction diminishes the concavitybetween the jaw and the side of the neck andproduces tense oblique ridges in the skin of

the neck. Platysma may assist in depressing the

mandible, and via its labial and modiolarattachments it can draw down the lower lip

and corners of the mouth in expressions ofhorror or surprise.

PLATYSMA 3/3 Action


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Muscles that form the floor of the oral cavity, superior view


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Origins and insertions on the mandible and hyoid

Muscles in the anterior triangle of the neck


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Muscles in the anterior triangle of the neck


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Borders and subdivisions of the anterior triangle of the neck


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Branches of the external carotid artery


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Muscles associated with the posterior triangle of the neck


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External jugular vein in the posterior triangle of the neck.


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Prevertebral and lateral muscles


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Fascialplanes of the

neck

The fascia of the neck has a number of


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The fascia of the neck has a number of

unique features.

The superficial fascia in the neck contains athin sheet of muscle (the platysma),

Platysma begins in the superficial fascia of

the thorax, runs upwards to attach to the mandible

and blend with the muscles on the face,

is innervated by the cervical branch of thefacial nerve [VII], and is only found in thislocation.


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Fascia of the neck, sagittal view


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Deep to the superficial fascia

the deep cervical fascia is organized into several distinct layers

1. an investing layer, which surrounds all structures in the neck;

2. the prevertebral layer, which surrounds the vertebral column

and the deep muscles associated with the back;

3. the pretracheal layer, which encloses the viscera of the neck;

4. the carotid sheaths, which receive a contribution from the other

three fascial layers and surround the two major neurovascular

bundles on either side of the neck.


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Prevertebral layer 1/3

The prevertebral layer is a cylindrical layer of fascia thatsurrounds the vertebral column and the musclesassociated with it (Fig. 8.152). Muscles in this groupinclude the prevertebral muscles, the anterior, middle,

and posterior scalene muscles, and the deep musclesof the back.

The prevertebral fascia is attached posteriorly alongthe length of the ligamentum nuchae, and superiorly

forms a continuous circular line attaching to the baseof the skull. This circle begins


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anteriorly as the fascia attaches to the basilar part ofthe occipital bone, the area of the jugular foramen, andthe carotid canal;

continues laterally, attaching to the mastoid process;

continues posteriorly along the superior nuchal lineending at the external occipital protuberance, where itassociates with its partner from the opposite side.

Anteriorly, the prevertebral column of fascia is

attached to the anterior surfaces of the transverseprocesses and bodies of vertebrae CI to CVII.



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The prevertebral fascia passing between theattachment points on the transverse processes isunique. In this location, it splits into two layers,creating a longitudinal fascial space containing looseconnective tissue that extends from the base of the

skull through the thorax. There is one additional specialization of the

prevertebral fascia in the lower region of the neck. Theprevertebral fascia in an anterolateral position extends

from the anterior and middle scalene muscles tosurround the brachial plexus and subclavian artery asthese structures pass into the axilla. This fascialextension is the axillary sheath.



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Pretracheal layer

The pretracheal layer consists of a collection of fascias thatsurround the trachea, esophagus, and thyroid gland (Fig.8.152). Anteriorly, it consists of a pretracheal fascia thatcrosses the neck, just posterior to the infrahyoid muscles,and covers the trachea and the thyroid gland. The

pretracheal fascia begins superiorly at the hyoid bone andends inferiorly in the upper thoracic cavity. Laterally, thisfascia continues and covers the thyroid gland and theesophagus.

posteriorly, the buccopharyngeal fascia forms the

pretracheal layer and separates the pharynx and theesophagus from the prevertebral layer.

The buccopharyngeal fascia begins superiorly at the base ofthe skull and ends inferiorly in the thoracic cavity.


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Carotid sheath

Each carotid sheath is a column of fascia thatsurrounds the common carotid artery, theinternal carotid artery, the internal jugular

vein, and the vagus nerve as these structurespass through the neck.

It receives contributions from the investing,prevertebral, and pretracheal layers, though

the extent of each component's contributionvaries


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Fascial compartments

The arrangement of the various layers of cervical fascia organizesthe neck into four longitudinal compartments:

the first compartment is the largest, includes the other three, andconsists of the area surrounded by the investing layer;

the second compartment consists of the vertebral column, the

deep muscles associated with this structure, and is the areacontained within the prevertebral layer;

the third compartment (the visceral compartment) contains thepharynx, the trachea, the esophagus, and the thyroid gland, whichare surrounded by the pretracheal layer;

finally, there is a compartment (the carotid sheath) consisting of the

neurovascular structures that pass from the base of the skull to thethoracic cavity, and the sheath enclosing these structures receivescontributions from the other cervical fascias

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Fascial spaces

Between the fascial layers in the neck are spaces that may provide a conduit forthe spread of infections from the neck to the mediastinum.

Three spaces could be involved in this process:

1. pretracheal space the first is the pretracheal space between the investing layerof cervical fascia (covering the posterior surface of the infrahyoid muscles) andthe pretracheal fascia (covering the anterior surface of the trachea and thethyroid gland), which passes between the neck and the anterior part of the

superior mediastinum;2. the second is the retropharyngeal space between the buccopharyngeal fascia

(on the posterior surface of the pharynx and esophagus) and the prevertebralfascia (on the anterior surface of the transverse processes and bodies of thecervical vertebrae), which extends from the base of the skull to the upper part ofthe posterior mediastinum

3. the third space is within the prevertebral layer covering the anterior surface ofthe transverse processes and bodies of the cervical vertebrae. This layer splitsinto two laminae to create a fascial space that begins at the base of the skull andextends through the posterior mediastinum to the diaphragm


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