School of Medical Sciences Neck

Cervical Fasciae

Root of Neck

Posterior Triangle of Neck

Anterior Triangle of Neck

Cervical Fasciae

deep fascia of neck condenses to form four layers: investing, pretracheal, prevertebral, and carotid sheath

Investing Layer

surrounds neck like collar
splits to enclose two muscles (trapezius & sternocleidomastoid), two salivary glands (parotid & submandibular) and two spaces (suprasternal & supraclavicular)
between angle of mandible and mastoid process, it splits into two laminae to enclose parotid gland, superficial lamina (parotid fascia) extends to zygomatic arch
deeper lamina (between angle of mandible and styloid process) forms stylomandibular ligament
forms roof of anterior and posterior triangles of neck

Attachments

sup: ext. occipital protuberance, sup nuchal line, mastoid process, lower border of mandible
inf: spine of scapula, acromion process, clavicle, manubrium
post: ligamentum nuchae, C7
ant: symphysis menti, hyoid bone

Pretracheal Fascia

lies deep to infrahyoids
splits to enclose thyroid, trachea and oesophagus

Attachments

sup: hyoid bone, thyroid cartilage, cricoid cartilage
inf: fibrous pericardium
lat: ant layer of carotid sheath

Prevertebral Fascia

situated in front of prevertebral muscles of neck (surrounds cervical vertebrae and associated muscles)
forms floor of post. triangle of neck
cervical and prox. brachial plexuses are deep to this fascia
axillary sheath is extension of this fascia

Attachments

sup: base of skull
inf: body of T4
inf & lat: axillary sheath

Carotid Sheath

encloses common carotid and internal carotid arteries, internal jugular vein, and vagus nerve
ansa cervicalis embedded in ant wall
sympathetic chain lies post, outside sheath
runs from base of skull to sup mediastinum

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Root of Neck

junctional area between neck and thorax
key structures: thoracic inlet, cervical pleura, scalenus anterior
oval shaped (transverse > A-P)
plane: oblique (post higher than ant)

Boundaries

post: T1
lat: 1st ribs and costal cartilages
ant: manubrium sterni

Arteries

right (r): brachiocephalic trunk, branches into r. subclavian and r. common carotid
left (l): l. subclavian, l. common carotid

Brachiocephalic Trunk

largest branch of arch of aorta, 4-5 cm in length and arises post to centre of manubrium
passes sup and to right, post to sternoclavicular joint where it divides into r. subclavian a. and r. common carotid a.
covered by sternohyoid and sternothyroid muscles

Subclavian

is divided into three parts by scalenus anterior, it gives the following branches:
Part 1 (med): vertebral, internal thoracic, thyrocervical trunk (® inf. thyroid, transverse cervical, suprascapular)
Part 2 (post): costocervical trunk (® sup intercostal, deep cervical)
Part 3 (lat): dorsal scapular, (occasionally suprascapular a)

Veins

subclavian (from axillary v.), anterior to scalenus anterior
internal and anterior jugular vv.

Anterior Jugular

smallest of jugular veins, usually paired (joined by jugular venous arch just sup to sternum)
arises near hyoid from confluence of submandibular veins (submental venous plexus)
descends in superf fascia between mid line and ant sternocleidomastoid, turns lat at root of neck and opens into termination of ext jugular

Nerves

phrenic n. (lat.)
vagus + recurrent laryngeal
sympathetic chain (med.)

Vagus

leaves skull through jugular foramen with internal jugular vein and CN IX and XI
descends in the carotid sheath
on right: vagus crosses origin of subclavian a. (post to brachiocephalic vein) and gives off recurrent laryngeal n. which loops back around subclavian
on left: recurrent laryngeal n. given off to loop around arch of aorta
after looping both recurrent laryngeal nn. ascends to reach inf pole of thyroid where they ascend in tracheoesophageal groove to supply all intrinsic muscles of larynx except cricothyroid

Phrenic Nerve

sole motor nerve to diaphragm
it arises from C3,4,5 nerves
it descends obliquely across the ant surface of scalenus ant, deep to prevertebral fascia
crosses between subclavian v and a.. to enter thorax

Sympathetic Chain

has three enlargements (ganglia), superior, middle, inferior
inf: lies at sup 1st rib, wrapped around vertebral a., usually fused with 1st thoracic ganglion
mid: lies on ant aspect of inf thyroid a. around level of cricoid cartilage (C6 vertebra)
sup: located at level of atlas and axis, large (2-3 cm long)

Lymphatics

left: thoracic duct
right: r. lymphatic duct receives jugular, subclavian and bronchomediastinal lymph trunks

Viscera

trachea
oesophagus
apex of lung with dome of pleura

Muscles

longus colli
sternal ends of sternocleidomastoid, sternohyoid, sternothyroid
scalene muscles

Ligament

ant. longitudinal lig.

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Posterior Triangle of Neck

triangular area in neck enclosed between sternocleidomastoid and trapezius

Boundaries

base: mid 1/3 of clavicle
apex: lies on sup. nuchal line
ant: post border of sternocleidomastoid
post: ant border of trapezius
roof: investing layer of cervical fascia
floor: prevertebral fascia fascia covering splenius capitus, levator scapulae, scalenus medius, and scalenus posterior

Nerves

spinal accessory, cervical plexus (including phrenic), brachial plexus
accessory n. (CN XI) divides post triangle into sup and inf parts, runs between sternocleidomastoid and trapezius (supplying both), enters at 1/3 way down sternocleidomastoid
lesser occipital n. (C2) ascends short distance along sternocleidomastoid before it divides to supply skin of neck and scalp post to auricle, and sup auricle
greater auricular n. (C2-3) curves over post sternocleidomastoid, supplies branches to skin of neck, divides into ant & post branch to supply inf auricle, and area from mastoid to mandible
transverse cervical n. (C2-3) curves around the post border of sternocleidomastoid near its middle, passes transversely across it, supplies skin of ant triangle of neck
supraclavicular nn. (C3-4) arise as single trunk, which divides into med, intermediate and lat branches
phrenic n. (C3-5) curves around lat border of scalenus ant, descends obliquely across ant surface, deep to transverse cervical and suprascapular aa., enters thorax by crossing origin of internal thoracic a. between subclavian a. & v.

Arteries

subclavian (3rd part), transverse cervical, suprascapular, occipital

Veins

external jugular, (subclavian)
pierces and fuses with investing cervical fascia about 5 cm above clavicle
if cut fascia prevents it from closing and can cause intravenous air embolus
lymph nodes
muscles

Muscle	Origin	Insertion	Innervation	Action
Splenius capitus	inf ligamentum nuchae, spinous processes of T1-T6	lat mastoid process and sup nuchal line	cervical spinal nn.	lat flexes head & neck, rotates head & neck to same side
Levator scapulae	transverse processes of C1-C4	sup med scapula	cervical spinal nn.	elevates scapula
Scalenus posterior	transverse process of C4-C6	2nd rib	cervical spinal nn.	lat flexes neck, elevates 2nd rib
Scalenus medius	transverse process of C2 & C7	sup post 1st rib	cervical spinal nn.	lat flexes neck, elevates 1st rib
Sterncleidomastoid	2 heads, sternal and clavicular	lat mastoid process, lat sup. nuchal line	CN XI	extend atlantio-occipital joint, flex cervical vertebrae

Subdivisions

inf belly of omohyoid splits post triangle into large occipital triangle and small supraclavicular triangle
occipital: occipital a. appears in its apex, contains important accessory n.
supraclavicular: location indicated on neck by supraclavicular fossa, crossed by subclavian a. and external jugular v.

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Anterior Triangle of Neck

anterior triangle = triangular area on front of neck

Boundaries

ant: midline
post: ant border of sternocleidomastoid
base: lower border of mandible, line drawn from angle of mandible to mastoid process
apex: jugular notch

muscles:
suprahyoid muscles: mylohyoid (floor of mouth), geniohyoid (reinforce floor of mouth), stylohyoid (small slip on each side), digastric (straplike, two bellies, intermediate tendon joined to hyoid)
infrahyoid muscles: omohyoid (two bellies, intermediate tendon joined to clavicle), sternohyoid (superf, except inf), sternothyroid (deep to sternohyoid), thyrohyoid (sup continuation of sternothyroid)

Muscle	Origin	Insertion	Innervation	Action
Mylohyoid	mylohyoid line of mandible	hyoid	mylohyoid n. (branch of V3 n.)	elevates hyoid, floor of mouth and tongue
Geniohyoid	inf mental spine of mandible	hyoid	C1 n	pulls hyoid ant-sup, shortens floor of mouth, widens pharynx
Stylohyoid	styloid process	hyoid	facial n.	elevates and retracts hyoid
Digastric	ant belly: mandible post belly: mastoid process	intermediate tendon: hyoid	ant belly: mylohyoid n. post belly: facial n.	depresses mandible, raises and steadies hyoid
Omohyoid	Sup border of scapula	hyoid	ansa cervicalis	depresses, retracts and steadies hyoid
Sternohyoid	manubrium and med clavicle	hyoid	ansa cervicalis	depresses hyoid
Sternothyroid	post surface ofmanubrium	thyroid cartilage	ansa cervicalis	depresses hyoid and larynx
Thyrohyoid	thyroid cartilage	hyoid	C1.	depresses hyoid and raises larynx

Arteries

common carotid, internal carotid, external carotid + branches

Veins

ant jugular, int jugular + tributaries

Nerves

(IX), X, XI , XII, ansa cervicalis, sympathetic trunk
viscera: pharynx, oesophagus, larynx, trachea
glands: parotid, submandibular, thyroid, parathyroid
submandibular fills most of digastric triangle, submandibular duct (5 cm) passes from deep process of gland to open on sublingual papilla

Subdivisions

sup belly of omohyoid and digastric muscles subdivide anterior triangle into four smaller triangles: submental, digastric, carotid, and muscular

		Submental	Digastric	Carotid	Muscular
Boundaries		median triangle situated between ant bellies of digastric muscles and hyoid bone floor: mylohyoid muscle	ant: ant digastric post: post digastric sup (base): base of ant triangle floor: mylohyoid, hyoglossus, part of mid constrictor of pharynx	ant-inf: sup omohyoid post: ant sternocleidomastoid sup: post digastric & stylohyoid floor: thyrohyoid, hyoglossus, mid & inf constrictors of pharynx	bounded by ant sternocleidomastoid, sup omohyoid, median plane floor: infrahyoid muscles
Contents	Arteries		facial vessels mylohyoid vessels submandibular vessels carotid sheath + contents	common carotid int & ext carotid + branches (sup thyroid, asc pharyngeal, lingual, facial, occipital, post auricular)
	Veins	submental		int jugular + tributaries (facial, pharyngeal, lingual, sup & mid thyroid)
	Nerves		mylohyoid nerves CN IX, X, XII	CN IX, X, XI ansa cervicalis sympathetic chain	ansa cervicalis
	Muscles		hyoglossus mylohyoid		infrahyoid muscles (sternohyoid, omohyoid, sternothyroid, thyrohyoid)
	Other	submental lymph nodes	submandibular gland lower part of parotid gland	deep cervical lymph nodes carotid body	neck viscera
Notes				carotid sinus (baroreceptor) dilation of prox int carotid a., innervated by sinus branch of glossopharyngeal carotid body lies (chemoreceptor) lies behind, also supplied by sinus branch best site to approach big blood vessels in neck	all infrahyoids supplied by ansa cervicalis, except for thyrohyoid, supplied by C1

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Midline of Neck

between infrahyoid muscles are number of structures in and adjoining midline of neck

hyoid bone
median thyrohyoid ligament
laryngeal prominence
cricothyroid ligament
cricoid cartilage
cricothyroid muscle
first tracheal ring
isthmus and pyramidal lobe of thyroid
inferior thyroid veins
jugular venous arch (joins two anterior jugular vv.)
thyroid ima a.

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Blood Vessels

Arteries

Common Carotid Arteries

r. common carotid begins at bifurcation of brachiocephalic, l. arises from arch of aorta (post to sternoclavicular joints)
ascends within carotid sheath to level of sup border of thyroid cartilage where it terminates by dividing into int & ext carotid aa.

Internal Carotid Artery

has no branches in neck, but are two of four major aa. that supply blood to brain
each passes vertically upwards from common to enter carotid canal in petrous part of temporal bone, accompanied by plexus of sympathetic fibres
during course through neck, lies deep to sternocleidomastoid m and parotid gland
enters middle cranial fossa through the superior part of foramen lacerum
supplies pituitary, orbit and most of supratentorial part of brain

External Carotid Artery

extends between C3/C4 vertebra to the neck of the mandible
runs midway between mastoid process and angle of mandible within the parotid gland
terminates by dividing into two branches, maxillary a. and superficial temporal a.

Branches of External Carotid Artery

Surface	Branch	Notes
Anterior	superior thyroid	arises close to origin of ext carotid, just inf to greater horn of hyoid runs ant-inf (deep to infrahyoids) to reach sup pole of thyroid also gives off muscular branches to sternocleidomastoid and infrahyoid muscles, and sup laryngeal a.
	Lingual	arises from ext carotid where it lies on mid constrictor of pharynx arches sup-ant at the level of greater horn of hyoid) and n passes deep to hypoglossal n., stylohyoid and post digastric disappears deep to hyoglossus muscle, then on genioglossus to becomes deep lingual a.
	Facial	arise from ext carotid just sup to the lingual a. gives off tonsillar branch and branches to palate passes sup (under stylohyoid, digastric ), loops ant and enters deep groove in submandibular gland crosses inf border of mandible and enters face
Posterior	Occipital	arises near level of facial a., passes post along inf border of post belly of digastric, ends in post part of scalp, during course pass superf to int carotid a. and CN IX, X and XI
Posterior	post auricular	arise at sup post belly of digastric, ascends post of ext auditory meatus and supplies adjacent muscles, parotid gland, facial n. and scalp
Medial	asc. Pharyngeal	ascends on pharynx (deep to int carotid) and sends branches to pharynx, prevertebral muscles, middle ear and meninges

Veins

Internal Jugular Vein

largest vein in neck (usually larger on right side than left)
drains blood from brain and superf part of face and neck
course corresponds to line drawn from external acoustic meatus to med end of clavicle
commences at jugular foramen in post cranial fossa, as direct continuation of sigmoid sinus, from dilation at origin (sup bulb of int jugular v.) it runs in carotid sheath, leaves ant triangle by passing deep to sternocleidomastoid and unites with subclavian post to med clavicle
inf bulb of int jugular v.
located near termination, contains bicuspid valve tributaries: petrosal sinus, facial, lingual, pharyngeal, sup and middle thyroid and often occipital vv.

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Thyroid Gland

largest of endocrine glands
consists of two lateral lobes, isthmus and occasionally pyramidal lobe
isthmus overlies 2nd, 3rd and 4th tracheal rings
med lat lobe overlies larynx, trachea, oesophagus, inf. constrictor of pharynx and cricothyroid muscles
post surface of lat lobe extends over carotid sheath
infrahyoid muscles cover gland anteriorly
levator glandulae thyroideae
attaches pyramidal lobe to hyoid bone, embryological remnant of thyroglossal duct
parathyroids
are situated on post border, along line of sup and inf thyroid aa. Anastomoses
arteries:
sup thyroid a. (from ext carotid a.); inf thyroid a. (from thyrocervical trunk); and occasionally thyroid ima a.(from arch of aorta).

Veins

sup and middle thyroid vv.(empty into int jug v); inf thyroid vv (empty into brachiocephal v)

Clinical

relation of isthmus to tracheal rings (tracheostomy)
relation of ext laryngeal n. with sup thyroid a. (ligation of artery during thyroidectomy, hoarseness of voice because cricothyroid paralysed)
relation of recurrent laryngeal n. with inf thyroid a. (ligation of artery during thyroidectomy, complete loss of voice as n. supplies all pharyngeal muscles except cricothyroid)
remnant of thyroglossal duct may give rise to cyst (always located along ant midline of neck)
close relationship of parathyroid to thyroid explain development of hypoparathyroidism is some patients following thyroidectomy

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Pharynx

funnel-shaped fibromuscular tube, common route for air and food
located post to nasal cavity, mouth and larynx
divided into three parts: nasopharynx, oropharynx, and laryngopharynx
it is about 15 cm in length, extends from base of skull to inf border of cricoid cartilage
widest (~5cm) opposite hyoid bone, narrowest (~1.5cm) at inf end
post wall lies against prevertral fasica, with potential retropharyngeal space in between
pharyngeal wall composed of five layers
mucous membrane
submucosa
pharyngobasilar fascia (attached to skull)
muscular layer composed of inner longitudinal (stylopharyngeus, palatopharyngeus and salpingopharyngeus) and outer ciruclar fibres (sup, middle and inf constrictors)
loose connective tissue layer forming buccopharyngeal fascia
supplied mainly by pharyngeal plexus of nn. (formed by CN IX (sensory) and X (motor)); nasopharynx receives its sensory supply mainly from CN V3

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Larynx

air conducting tube, measures ~ 5 cm in length
located in front of C3-C6 vertebrae below the hyoid bone
cartilages: 3 single (epiglottis, thyroid, cricoid); 3 paired (arytenoid, corniculate, cuneiform)
membranes and ligaments:
extrinsic: thyrohyoid membrane, cricotracheal membrane
intrinsic: quadrangular membrane (extends between epiglottis and vestibular folds); cricovocal membrane (extends between vocal ligament and upper border of cricoid cartilage)

Cavity

divided into three parts:
upper (vestibular) part; middle (ventricular) part: between vestibular and vocal folds; and lower (infraglottic) part
rima glottidis: is the aperture between the two vocal folds.

Muscles of the Larynx

extrinsic muscles that move the larynx up and down during deglutition:
elevators of larynx : digastric, stylohyoid, mylohyoid, and geniohyoid muscles
depressors of larynx : sternohyoid, sternothyroid, and omohyoid muscles
instrinsic muscles: these are small muscles that move parts of the larynx on each other, and are particularly concerned with alterations in the length and tension of vocal folds in the production of voice, and in changing the size of rima glottidis to facilitate entry of air to the lungs

Nerves of the Larynx

sensory nerve supply (to the mucosa) : above vocal fold: internal laryngeal nerve vocal fold: recurrent laryngeal nerve
motor nerve supply (to intrinsic muscles) : recurrent laryngeal nerve, except for cricothyroid (supplied by external laryngeal nerve)

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