Download THE NECK BONES Skeleton is formed by cervical vertebrae, hyoid

THE NECK
BONES






Skeleton is formed by cervical vertebrae, hyoid bone, manubrium of sternum, clavicles
o
All of these are part of the axial skeleton, except for the clavicles, which are appendicular
CERVICAL VERTEBRAE
o
3rd-6th cervicals have the following characteristics

Vertebral body is small and longer from side to side than anteroposteriorly; the superior
surface is concave, and the inferior surface is convex

Vertebral foramen is large and triangular

Transverse processes of all cervical vertebrae have foramina transversaria for arteries
and veins

C7 only has for veins though

Superior facets of articular processes are directed superoposteriorly, and inferior facets
are directed inferoposteriorly

Spinous processes are short and bifid in individuals of European heritage
o
3 atypical cervical vertebrae

ATLAS

AXIS

VERTEBRA PROMINENS (C7)
HYOID BONE
o
At the level of the C3 vertebra
o
Serves as an attachment for anterior neck muscles and a prop to keep the airway open
CERVICAL PAIN
o
Metastases from the thorax and head may go into the cervical nodes
o
Most chronic cervical pain is due to bony abnormalities or trauma
INJURIES OF CERVICAL COLUMN
o
Fractures and dislocations of the cervical vertebrae may injure spinal cord or vertebral arteries,
sympathetic plexuses passing through the foramina transversaria
FRACTURE OF HYOID BONE
o
Occurs in people who are manually strangled by compression of the throat
o
Inability to elevate hyoid and move it beneath the tongue makes swallowing and separation of
the alimentary and respiratory tracts difficult
o
May result in aspiration pneumonia
FASCIA OF NECK



Fascial planes determine where an infection might spread
CERVICAL SUBQ TISSUE AND PLATYSMA
o
Layer of fatty CT between dermis of skin and investing layer of deep cervical fascia
o
Contains cutaneous nerves, blood, lymphatic vessels, superficial lymph nodes, fat
o
Anterolaterally, contains the platysma

Broad thin sheet of muscle in the subq tissue of neck

Derives from mesenchyme in 2nd pharyngeal arch of the embryo and is supplied by
cervical branch of FACIAL NERVE (VII)

External jugular vein, and main cutaneous nerves of neck are deep to the platysma

Fibers arise from deep fascia covering superior parts of the deltoid and pectoralis major
muscles and go to inferior border of mandible
o
Suprasternal space lies between two layers of this fascia—one layer attaches to anterior part of
manubrium, the other to posterior part of manubrium

Encloses inferior ends of the anterior jugular veins, the jugular venous arch, fat, and a
few deep lymph nodes
PRETRACHEAL LAYER OF DEEP CERVICAL FASCIA
o
Limited to anterior part of neck
o
Extends inferiorly from hyoid into thorax, where it blends with fibrous pericardium covering the
heart
Includes thin muscular part enclosing infrahyoid muscles and a visceral part which encloses
thyroid gland, trachea, and esophagus

Continuous posteriorly and superiorly with buccopharyngeal fascia of the pharynx
o
Blends laterally with carotid sheaths
o
Superior to hyoid, a thickening of the pretracheal fascia forms a pulley or trochlea through which
the intermediate tendon of the digastric muscle passes, suspending hyoid
o
Also tethers the omohyoid muscle by wrapping around the lateral border of the intermediate
tendon of this muscle

Redirects the course of this muscle between the bellies
PREVERTEBRAL LAYER OF DEEP CERVICAL FASCIA
o
Forms a tubular sheath for the vertebral column and muscles associated with it

Longus colli, longus capitis, scalenes, deep cervical muscles
o
This is fixed to the cranial base superiorly
o
Blends with endothoracic fascia inferiorly and fuses with anterior longitudinal ligament at the T3
vertebra
o
Extends laterally as the axillary sheath which covers brachial plexus
o
Cervical parts of the sympathetic trunks are embedded in this fascia
CAROTID SHEATH
o
Extends from cranial base to root of the neck
o
Blends anteriorly with investing and pretracheal layers of fascia and posteriorly with prevertebral
layer of fascia
o
Contains

COMMON AND INTERNAL CAROTID ARTERIES

INTERNAL JUGULAR VEIN

VAGUS NERVE

DEEP CERVICAL LYMPH NODES

CAROTID SINUS NERVE

SYMPATHETIC NERVE FIBERS (CAROTID PERIARTERIAL PLEXUSES)
o
This and the pretracheal fascia communicate freely with the mediastinum of the thorax inferiorly
and cranial cavity superiorly
RETROPHARYNGEAL SPACE
o
Largest and most important interfascial space in the neck
o
Potential space with loose connective tissue between the visceral part of the prevertebral layer of
deep cervical fascia and the buccopharyngeal fascia surrounding the pharynx superficially
o
Inferiorly, the buccopharyngeal fascia is continuous with pretracheal layer of deep cervical fascia
o
alar fascia is another subdivision of this space – attached along the midline of the
buccopharyngeal fascia from cranium to level of C7 vertebra

extends laterally and terminates in carotid sheath
o
this space allows the pharynx, esophagus, larynx, trachea to move relative to vertebral column
during swallowing
o
closed superiorly by cranial base and on each side by carotid sheath
o
opens inferiorly into superior mediastinum
PARALYSIS OF PLATYSMA
o
Causes skin to fall away from neck in folds
o
Is caused by damage to cervical branch of facial nerve
SPREAD OF INFECTION IN NECK
o
Investing layer of deep cervical fascia helps prevent the spread of abscesses
o
If the infection spreads between investing fascia and visceral part of pretracheal fascia – it can
spread to thoracic cavity anterior to pericardium
o
Pus from abscess posterior to the prevertebral layer of deep cervical fascia may extend laterally
in the neck and form a swelling posterior to SCM
o
Perforation of the prevertebral layer and entrance of retropharyngeal space ensues, producing a
retropharyngeal abscess (bulge in the pharynx)

May cause difficulty swallowing and speaking
o
Air from a ruptured trachea, bronchus, or esophagus can also pass into the neck
(pneumomediastinum)
o





SUPERFICIAL STRUCTURES OF NECK – CERVICAL REGIONS



STERNOCLEIDOMASTOID REGION
o
SCM is a key landmark

divides each side of the neck into anterior and lateral cervical regions (anterior and
posterior triangles)

has two heads

sternal head (to manubrium)

clavicular head (medial part of clavicle)

separated inferiorly by a space – lesser supraclavicular fossa

attaches superiorly to mastoid process of temporal bone and the superior nuchal line of
the occipital bone

flex head, extend at OA joint, and act as accessory respiratory muscles
POSTERIOR CERVICAL REGION
o
Trapezius is the main muscle here
LATERAL CERVICAL REGION
o
Aka posterior triangle
o
Bounded by SCM, trap, clavicle, where SCM and trap meet at superior nuchal line
o
Roof is made up of investing layer of deep cervical fascia
o
Floor is formed by muscles covered by the prevertebral layer of deep cervical fascia

Splenius capitis, levator scapulae, middle scalene, posterior scalene; anterior scalene is
hidden by SCM
o
Lateral cervical region is divided into two triangles:

Occipital triangle

CN XI crosses here

Occipital a at apex

Omoclavicular (subclavian) triangle is indicated by supraclavicular fossa

Inferior part of external jugular vein crosses this triangle superficially

Subclavian a lies deep to it

Triangles are separated by inferior belly of omohyoid
o
ARTERIES IN LATERAL CERVICAL REGION

Include lateral branches of thyrocervical trunk, third part of subclavian artery, and part
of occipital artery

Thyrocervical trunk gives rise to suprascapular artery and cervicodorsal trunk

Terminal branches are ascending cervical and inferior thyroid artery

Suprascapular artery passes across scalenes and phrenic nerve
o
Supplies muscles on posterior part of scapula
o
Suprascapular artery may also come of the third part of subclavian
directly

Cervicodorsal trunk (aka transverse cervical artery)
o
Bifurcates to superficial cervical artery and dorsal scapular artery
o
Supply vasa vasorum of brachial plexus
o
Superficial cervical artery goes with CN XI
o
Dorsal scapular artery runs deep to levator scapulae and deep to
rhomboids, supplying both and anastomosing around the scapula

Occipital artery, a branch of external carotid artery, enters lateral cervical
region at its apex and ascends over the head to supply the posterior half of the
scalp

Third part of subclavian artery supplies blood to upper limb—lies over the 1st rib
o
VEINS IN LATERAL CERVICAL REGION

External jugular vein

Originates from retromandibular vein and posterior auricular vein

Pierces investing layer of deep cervical fascia and terminates in subclavian vein

Drains most of scalp and side of face

Receives cervicodorsal, suprascapular, and anterior jugular veins just superior
to clavicle

Subclavian vein drains upper limb

Passes anterior to scalene muscle and phrenic nerve and unites at the medial
border of the muscle with internal jugular vein to form brachiocephalic vein
o
NERVES OF LATERAL CERVICAL REGION
Spinal accessory nerve
Roots of brachial plexus

(C5-C8, T1)

Suprascapular nerve

Arises from superior trunk of brachial plexus

Supplies supraspinatus and infraspinatus

Roots of cervical plexus

C1-C4

Lies anteromedial to levator scapulae and middle scalene and deep to SCM

Superior root of ansa cervicalis (C1/C2) joins and descends from hypoglossal
nerve as it traverses lateral cervical region

Ansa cervicalis

Inferior root of ansa cervicalis arises from a loop between spinal nerves C2/C3

Superior and inferior roots of ansa cervicalis unite, forming a secondary loop—
ansa cervicalis
o
Consists of C1-C3 spinal nerves
o
Supply infrahyoid muscles—omohyoid, sternothyroid, and sternohyoid

Thyrohyoid (4th infrahyoid muscle) gets C1 fibers, which
descend independently from hypoglossal nerve

Cutaneous branches of cervical plexus supply skin of neck, superolateral
thoracic wall, and scalp

Superior cervical ganglion gives sympathetic fibers (gray rami communicantes)
to roots

Branches of cervical plexus

Lesser occipital nerve
o
Supplies skin of neck and scalp posterosuperior to auricle

Great auricular nerve
o
(C2-C3)
o
Divides and supplies skin over and sheath surrounding parotid gland,
mastoid process, and both surfaces of the auricle and an area of skin
extending from angle of mandible to mastoid process

Transverse cervical nerve (C2-C3)
o
Supplies skin over anterior cervical region

Supraclavicular nerves (C3-C4)
o
Branch to skin of neck that cross the clavicle and supply skin over
shoulder

DEEP MOTOR BRANCHES
o
Include branches of roots supplying the rhomboids, serratus anterior,
and nearby prevertebral muscles

PHRENIC NERVES
o
Originate chiefly from C4 nerve but receive contributions from C3 and
C5 nerves
o
Contain motor, sensory, and sympathetic nerve fibers
o
Sole supply to diaphragm and sensation to its central part
o
Runs posterior to the subclavian vein and anterior to the internal
thoracic artery as it enters the thorax
o
LYMPH NODES IN LATERAL CERVICAL REGION

Superficial cervical lymph nodes lie superficial to the SCM

These drain to deep cervical nodes which form a chain along the course of the internal
jugular vein embedded in the fascia of the carotid sheath
ANTERIOR CERVICAL REGION
o
Anterior boundary is formed by the median line of the neck
o
Posterior boundary is formed by the anterior border of SCM
o
Superior boundary is formed by inferior border of mandible
o
Apex located at jugular notch in the manubrium
o
Roof formed by subQ tissue containing platysma
o
Floor formed by pharynx, larynx, and thyroid gland
o
Is divided into four smaller triangles by digastric and omohyoid muscles



o
o
o
o
o
SUBMENTAL TRIANGLE

Inferior to chin; suprahyoid area bounded inferiorly by body of hyoid and laterally by
right and left anterior bellies of the digastric muscles

Floor of submental triangle is formed by two mylohyoid muscles, which meet in a
median FIBROUS RAPHE

Apex of submental triangle is at mandibular symphysis

Contains LYMPH NODES, small veins meeting to form ANTERIOR JUGULAR VEIN
SUBMANDIBULAR TRIANGLE

Between inferior border of mandible and anterior and posterior bellies of the digastric
muscle

Floor of this triangle is formed by mylohyoid and hyoglossus muscles and middle
pharyngeal constrictor

Contains SUBMANDIBULAR GLAND and SUBMANDIBULAR LYMPH NODES and
HYPOGLOSSAL NERVE and NERVE TO MYLOHYOID MUSCLE (a branch of CN V3, which
also supplies the anterior belly of digastric muscle), parts of FACIAL ARTERY AND VEIN,
and SUBMENTAL ARTERY (branch off facial artery)
CAROTID TRIANGLE

Bounded by superior belly of omohyoid, posterior belly of digastric, and anterior border
of SCM

COMMON CAROTID ARTERY ascends into it

Divides into internal and external carotid arteries

CAROTID SINUS is located inside

Innervated by glossopharyngeal nerve, through carotid sinus nerve as well as
by vagus nerve

This is a baroreceptor that reacts to changes in arterial blood pressure

CAROTID BODY

Small, reddish brown mass of tissue that lies on medial side of bifurcation of
common carotid artery
o
Closely related to carotid sinus
o
Supplied by carotid sinus nerve (IX) and CN X

This is a chemoreceptor that monitors levels of O2 in the blood

Initiates increase in rate and depth of respiration, cardiac rate, and blood
pressure

Neurovascular structures here surrounded by carotid sheath—carotid arteries medially,
internal jugular vein laterally, and vagus nerve posteriorly
MUSCULAR TRIANGLE

Bounded by superior belly of the omohyoid muscle, anterior border of SCM, and median
plane of neck

Contains INFRAHYOID MUSCLES and VISCERA (thyroid and parathyroid glands)
MUSCLES IN ANTERIOR CERVICAL REGION

Hyoid provides attachments for suprahyoid and infrahyoid muscles

These muscles steady the hyoid and larynx

SUPRAHYOID MUSCLES

Superior to hyoid and connect it to cranium

MYLOHYOID

GENIOHYOID

STYLOHYOID

DIGASTRIC
o
Has two bellies, joined by intermediate tendon that descends towards
hyoid
o
Fibrous sling from pretracheal layer of deep fascia allows the tendon to
slide anteriorly and posteriorly as it connects this tendon to the body
and greater horn of the hyoid
o
The two bellies have two different nerve supplies because they have
different embryologic origin

From 1st and 2nd pharyngeal arches

CN V supplies derivatives of 1st arch (anterior belly)

CN VII supplies 2nd arch (posterior belly)

o
The point of them is to make the floor of the mouth, support the hyoid, and
provide a base from which the tongue functions

They also elevate hyoid and larynx in relation to swallowing and tone roid
cartilage immediately superior to the production

INFRAHYOID MUSCLES

Are called strap muscles and are inferior to hyoid

These anchor the hyoid, sternum, clavicle, and scapula and depress the hyoid
and larynx during swallowing and speaking

They also steady the hyoid with the suprahyoid muscles—provides a firm base
for the tongue

Are arranged in two planes – superficial (sternohyoid and omohyoid) and deep
(sternothyroid and thyrohyoid)

STERNOTHYROID
o
Is wider than sternohyoid, under which it lies
o
Covers lateral lobe of thyroid gland
o
Attachment to oblique line of lamina of the thyroid cartilage
immediately superior to the gland limits upward extension of an
enlarged thyroid

THYROHYOID
o
Appears to be continuation of sternothyroid muscle, running superiorly
from oblique line of thyroid cartilage to the hyoid
ARTERIES IN ANTERIOR CERVICAL REGION

Contains carotid system of arteries, consisting of common carotid artery and its terminal
branches—internal and external carotid arteries

Also contains internal jugular vein and its tributaries and anterior jugular veins

Right common carotid artery begins at bifurcation of brachiocephalic trunk

Right subclavian artery is the other branch of this trunk

Left common carotid artery comes off the arch of aorta

The left common carotid has a course of approximately 2 cm in the superior
mediastinum before entering the neck

Internal carotid arteries

Proximal part is the site of carotid sinus

Carotid body is located in the cleft between the internal and external carotid
arteries

These enter the cranium through the carotid canals in the petrous temporal
bones
o
NO NAMED ARTERIES ARISE FROM ICA IN THE NECK

External carotid arteries

Supply most structures external to the skull
o
The orbit and scalp supplied by the supraorbital artery are the major
exceptions

Middle meningeal artery comes off this as well

External carotid artery embeds itself in the parotid gland and terminates by
dividing into two branches—maxillary artery and superficial temporal artery
o
Before these terminal branches, six arteries arise off the ECA

ASCENDING PHARYNGEAL ARTERY

First or second branch off ECA and is its only medial
branch

Sends branches to pharynx, prevertebral muscles,
middle ear, and cranial meninges

OCCIPITAL ARTERY

Comes off posterior aspect of ECA, superior to origin
of facial artery

Passes immediately parallel to attachment of
posterior belly of digastric muscle in the OCCIPITAL
GROOVE in the temporal bone

Divides into many branches in the scalp

POSTERIOR AURICULAR ARTERY

o
o
o
Small posterior branch of ECA, which is usually the
last preterminal branch

Ascends posterior between the external acoustic
meatus and mastoid process to supply the adjacent
muscles; parotid gland; facial nerve; structures in
temporal bone; auricle; scalp

SUPERIOR THYROID ARTERY

Most inferior of three anterior branches of ECA

Goes to thyroid gland

Also supplies infrahyoid muscles and SCM and gives
rise to superior laryngeal artery, supplying the larynx

LINGUAL ARTERY

Arises from anterior aspect of ECA

Lies on the middle pharyngeal constrictor

Arches superoanteriorly and passes deep to
hypoglossal nerve, stylohyoid muscle, and posterior
belly of digastric muscle

Gives branches to posterior tongue

Bifurcates into deep lingual and sublingual arteries

FACIAL ARTERY

Arises anteriorly from ECA, either in common with
lingual artery or immediately superior to it

Gives rise to ascending palatine artery and a tonsillar
branch

Passes superiorly under cover of digastric and
stylohyoid muscles and the angle of mandible

Supplies submandibular gland

Gives rise to submental artery and hooks around the
middle of the inferior border of the mandible to enter
the face
o
MNEMONIC—1, 2, 3

One branch arises medially off ECA—ascending pharyngeal

Two branches arise posteriorly—occipital and posterior
auricular

Three branches arise anteriorly—superior thyroid, lingual, and
facial
VEINS IN ANTERIOR CERVICAL REGION

Most veins in anterior cervical region are tributaries of the internal jugular vein, typically
the largest vein in the neck

IJV drains blood from brain, anterior face, cervical viscera, and deep muscles of neck

Inferior end of the IJV passes deep to the gap between heads of the SCM

IJV merges with subclavian to make BRACHIOCEPHALIC VEIN

Starts at jugular foramen in the posterior cranial fossa as direct continuation of sigmoid
sinus

SUPERIOR BULB OF IJV—vein descends in carotid sheath

INFERIOR BULB OF IJV

Has a bicuspid valve that allows blood to flow toward the heart while preventing
backflow into vein, as might occur if inverted

Tributaries of IJV are inferior petrosal sinus, facial, lingual, pharyngeal, superior and
middle thyroid veins

OCCIPITAL VEIN usually drains into suboccipital venous plexus, drained by deep cervical
vein and the vertebral vein, but it may drain into IJV directly
CERVICAL SYMPATHETIC TRUNK

Lies posterior to carotid sheath

Trunk is not within the sheath—it is embedded in the prevertebral layer of cervical fascia
NERVES IN ANTERIOR CERVICAL REGION

Several nerves, including branches of CNs are in this region

TRANSVERSE CERVICAL NERVE (C2/C3)

Supplies skin covering anterior cervical region
HYPOGLOSSAL NERVE

Motor nerve of tongue

Is in submandibular triangle—supplies 4/5 extrinsic tongue muscles

GLOSSOPHARYNGEAL and VAGUS NERVES

In submandibular and carotid triangles

Glossopharyngeal is primarily related to tongue and pharynx

Vagus nerve gives rise to pharyngeal, laryngeal, and cardiac branches
Supraclavicular fossa – subclavian arterial pulsations can be felt here


CONGENITAL TORTICOLLIS
o
o
o
Contraction or shortening of cervical muscles that produces twisting of the neck and slanting of the head—
torticollis
Most common type results from a fibrous tissue tumor that develops in SCM before or shortly after birth
You can also damage the SCM when pulling infant’s head too much during difficult birth
o
Torticollis develops due to subsequent hematoma
o
May also damage the branch of CN XI that innervates SCM
SPASMODIC TORTICOLLIS
o
o
Cervical dystonia (abnormal tonicity of cervical muscles) begins in adulthood
o
Also known as spasmodic torticollis
Involves any bilateral combination of lateral neck muscles, especially SCM and trapezius
SUBCLAVIAN VEIN PUNCTURE
o
o
o
o
o
CENTRAL LINE PLACEMENT—right or left subclavian vein is the point of entry to the venous system
Used to administer parenteral (venous nutritional) fluids and medications and to measure central venous
pressure
How to do
o
Place thumb on middle part of clavicle and index finger on the jugular notch in the manubrium
o
Needle punctures skin inferior to thumb (middle of clavicle) and is advanced medially towards the
tip of the index finger (jugular notch) until the tip enters the right venous angle, posterior to the
sternoclavicular joint
o
Here the internal jugular and subclavian veins merge to make brachiocephalic vein
If you don’t do it right, you could puncture a lung (pneumothorax), or the subclavian artery
Once the needle is inserted into the subclavian vein, a soft flexible catheter is brought into it, using the
needle as a guide
RIGHT CARDIAC CATHETERIZATION
o
o
o
Used to take measurements of pressures in the right chambers of heart
Puncture of IJV can be used to introduce a catheter through the right brachiocephalic vein into superior
vena cava and the right side of the heart
Sometimes it’s necessary to use EJV instead
o
It is not ideal because its angle of junction with subclavian vein makes passage of catheter
difficult
PROMINENCE OF EXTERNAL JUGULAR VEIN
o
o
o
EJV serves as internal barometer
When venous pressure is in the normal range, EJV is visible above the clavicle for only a short distance
But when venous pressure rises (heart failure) vein is prominent throughout its course on the side of the
neck
SEVERANCE OF EXTERNAL JUGULAR VEIN
o
o
o
If EJV is severed along posterior border of SCM, its lumen is held open by the tough investing layer of
deep cervical fascia, and the negative intrathoracic pressure air will such air into the vein
Venous embolism develops and person turns blue (cyanosis) due to excessive concentration of reduced Hb
in the blood
Froth develops in the heart, which stops blood flow and results in dyspnea
LESIONS OF SPINAL ACCESSORY NERVE
o
o
o
You can fracture your jugular foramen and get a lesion of CN XI as it leaves the foramen
Lesions of this nerve result in trapezius and SCM atrophy
CN XI is the most common iatrogenic nerve injury
SEVERANCE OF PHRENIC NERVES/PHRENIC NERVE BLOCK/CRUSH
o
Severance of phrenic nerve results in paralysis of half the diaphragm
NERVE BLOCKS IN LATERAL CERVICAL REGION
o
o
o
o
o
Cervical plexus block inhibits nerve impulse conduction
NERVE POINT OF THE NECK—where anesthetic agent is given at the junction of SCM’s superior and middle
thirds
This procedure is not performed if you have cardiac or pulmonary disease b/c it involves the phrenic nerve
For anesthesia of upper limb, the anesthetic agent in a supraclavicular brachial plexus block is injected
around the supraclavicular part of the brachial plexus
Superior to the midpoint of the clavicle—site of injection
INJURY TO SUPRASCAPULAR NERVE
o
o
o
o
Vulnerable to injury in fractures of the middle third of clavicle
Results in loss of lateral rotation of the humerus at the glenohumeral joint
Limb rotates medially when relaxed—waiter’s tip position
Ability to initiate abduction is also affected
LIGATION OF ECA
o
o
o
o
Sometimes needed to control bleeding from one of its inaccessible branches
Does not eliminate blood flow however
Blood flows in a retrograde direction into the artery from the external carotid artery on the other side
through communications between its branches and across the midline
Descending branch of occipital artery provides the main collateral circulation, anastomosing with the
vertebral and deep cervical arteries
SURGICAL DISSECTION OF CAROTID TRIANGLE
o
o
Provides an important surgical approach to carotid systems of arteries
Provides access to IJV, vagus, and hypoglossal nerves, and cervical sympathetic trunk
CAROTID OCCLUSION AND ENDARTERECTOMY
o
o
o
o
Occlusion of ICA via atherosclerotic plaque may result in TIA or stroke
Carotid endarterectomy can strip off atherosclerotic plaques
After operation drugs inhibiting clot formation are given until endothelium has regrown
There is a risk of CN injury in this operation – IX, X, XI, XII