School of Medical Sciences


Neck

Table of Contents


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
Top

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

Contents

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.
Top

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

Contents

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.
Top

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

Contents

  • 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

Top

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.
Top

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

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.
Top

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
Top

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
Top

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)
Top