Anatomy of Head and Neck

HEAD AND NECK

Crisle Dychingco, MD, DPBS

Department of Anatomy

AUFSOM

Skeleton of the Head• Mastoid process• Styloid process• External auditory/

acoustic meatus

(ear opening)• Ear drum• Hyoid bone• Epiglottis• Thryroid cartilage• Cricoid cartilage• Tracheal rings

Neck

• Neck is anatomically complex• Vertebral compartment – cervical (=neck) vertebrae and muscles• Visceral compartment – parts of respiratory and digestive tracts, and

some endocrine organs• Vascular compartments – major blood vessels of head and neck

Anterior and posterior triangles of neck

• Aid regional description of anatomy• Anterior and posterior triangles separated by sternocleidomastoid

Platysma muscle• Muscle of facial expression in superficial fascia (subcutaneous)• Supplied by facial nerve (CN VII), cervical branch

Netter 21, Moore&Agur 597

Dermatomes of neck

• Dermatome: area of skin supplied by cutaneous branches derived from a single spinal nerve

• C2-C4, also C5 posteriorly• Adjacent dermatomes overlap

Netter 150, 155

Cutaneous nerves of neck

• Spinal nerves branch into dorsal and ventral rami

• Posteriorly: dorsal rami of spinal nerves C2 or C3 - C5

• Anteriorly: branches of cervical plexus from ventral rami of C2 - C4– Lesser occipital, great auricular,

transverse cervical, supraclavicular

Net

ter

18, 1

56

Deep fascia of neck

• Investing (superficial) layer• Visceral (pretracheal/buccopharyngeal) layer• Prevertebral layer• Carotid sheath• Retropharyngeal space

Netter 30

Posterior triangle of neck

• Borders: SCM, trapezius, middle 1/3 of clavicle• Roof: investing layer of deep cervical fascia• Floor: prevertebral fascia and deep muscles of neck• Surface anatomy: supraclavicular fossa, CN XI

Netter 18Backhouse 57

Sternocleidomastoid muscle

• Individually: laterally flexes (abducts) head/neck to same side, laterally rotates head/neck to opposite side

• Together: flexes head/neck•

Netter 23, Devinsky 41, 43

Trapezius muscle

• Elevate, retract, depress shoulder girdle• Lateral rotation of scapula (aids abduction of upper limb)

Netter 160, Devinsky 45

Innervation of SCM and trapezius: CN XI

• (spinal) accessory nerve (CN XI)

Netter 121, Fix 19

Floor of posterior triangle of neck• Splenius, levator scapulae, scalenes (posterior, middle,

anterior)• Anterior to anterior scalene: phrenic n, subclavian v, IJV,

inferior belly of omohyoid• Between anterior and middle scalenes: brachial plexus

(ventral rami, trunks), subclavian artery

Net

ter

22, 2

8

Anterior triangle of neck

• Borders: SCM, midline, mandible• Roof: investing layer of deep cervical fascia• Floor: pretracheal fascia over viscera of neck

Netter 22,23

Subtriangles in anterior triangle of neck

• Submandibular, submental, carotid, muscular • Additional borders: digastric, omohyoid muscles; hyoid bone

Netter 22,23

Submandibular, submental triangles• Hyoid bone• Digastric, stylohyoid muscles • Mylohyoid - floor of mouth• Submandibular salivary gland, facial and lingual

aa,vv, hypoglossal n

Netter 22,63

Infrahyoid (strap) muscles• Sternohyoid, omohyoid; sternothyroid, thyrohyoid• Action: depress hyoid and larynx after swallowing, help stabilise hyoid

bone• Carotid D

– Common carotid bifurcation; IJV

• Muscular D– Viscera of neck

Netter 24

Contents of carotid sheath

• Location: in carotid triangle superiorly, deep to SCM inferiorly

• Common (and internal) carotid artery• Internal jugular vein• Vagus nerve• Deep cervical lymph nodes

Netter 30, 24

Autonomic nerves in neck• Vagus nerve - in carotid

sheath• Sympathetic chain: superior

and middle cervical ganglia, cervicothoracic (stellate) ganglion Netter 30, 124

Viscera of neck• Larynx (thyroid, cricoid cartilages) and trachea• Pharynx and oesophagus• Thyroid and parathyroid glands

Netter 30, 68b

Thyroid, parathyroid glands• Thyroid: isthmus (midline), right and left lobes,

pyramidal lobe• Parathyroids: superior and inferior, on posterior

surface of thyroid

Netter 26, 68,70

Blood supply to thyroid, parathyroids• Superior, inferior thyroid artery• Superior, middle, inferior thyroid veins• Note relationships to laryngeal nerves

Netter 68,69

Common Carotid Artery• Right Common Carotid Artery

– from brachiocephalic a behind R sternoclavicular joint

• Left Common Carotid Artery– from arch of aorta

• Both run upward through the neck in the carotid sheath

• Under cover by anterior border of SCM

• Divides into ICA and ECA at the upper border of thyroid cartilage

• Laterally: internal jugular vein (vagus n between)

Posterior View

Common Carotid Artery• Carotid Sinus

– Localized dilatation of CCA– Located at point of division– Bulbous– 2 cm long– Supplied by glossopharyngeal

n (sinus nerve of Hering)– Pressoreceptor, baroreceptor– Assists in regulation of BP

Common Carotid Artery

• Carotid Body– Small neurovascular

structure posterior to point of division

– Supplied by glossopharyngeal n

– Chemoreceptor– Sensitive to excess CO2

and reduced O2 tension in blood

– Assists in regulating heart and respiratory rates

Branches of the CCA

EXTERNAL CAROTID ARTERY

• one of terminal branches of CCA

• from the level of upper border of thyroid cartilage

• ascends to terminate in parotid gland behind neck of mandible

• divides into superficial temporal and maxillary aa

INTERNAL CAROTID ARTERY

• ascends with internal jugular v and vagus n

• passes deep into parotid gland

• enters cranial cavity via carotid canal in petrous part of temporal bone

• terminate by dividing into anterior and middle cerebral aa

External Carotid Artery

• Superior thyroid artery• Ascending pharyngeal

artery• Lingual artery• Facial artery• Occipital artery• Posterior auricular

artery• Superficial temporal

artery• Maxillary artery

"Some Angry Lady Figured Out PMS":Superior thyroidAscending pharyngealLingualFacialOccipitalPosterior auricularMaxillarySuperificial temporal

SUPERIOR THYROID ARTERY

• Curves downward to upper pole of thyroid gland

• Accompanied by external laryngeal nerve (cricothyroid m)

ASCENDING PHARYNGEAL ARTERY

• ascends along and supplies the pharyngeal wall

LINGUAL ARTERY

• loops upward and forward

• Crossed superficially by hypoglossal nerve

FACIAL ARTERY• loops upward on lateral

surface of pharynx close to the tonsil

• tunnels the submandibular gland

• bends around lower border of mandible

• ascends close to anterior border of masseter

• ascends lateral to mouth• terminates at medial angle of

orbit• pulsations felt against the

mandible• branches supply: tonsil,

submandibular gland, muscles and skin of face

OCCIPITAL ARTERY• supplies the back of the

scalp

POSTERIOR AURICULAR ARTERY

• auricle and scalp

SUPERFICIAL TEMPORAL ARTERY

• ascends over zygomatic arch

• palpated in front of auricle

• accompanied by auriculotemporal nerve

• supplies the scalp

MAXILLARY ARTERY

• Runs forward medial to neck of mandible

• Splits into branches that follow maxillary branches of trigeminal nerve

• Supply upper and lower jaws, muscles of mastication, nose, palate and meninges

MAXILLARY ARTERYMiddle meningeal artery • ascends between roots of auriculotemporal

nerve to enter skull via foramen spinosum• Runs laterally within skull and divides into

anterior and posterior branches• Anterior branch

– lies close to motor area of cerebral cortex– alongside its vein, grooves the upper part of

greater wing of sphenoid bone and anteroinferior angle of parietal bone (prone to trauma)

– lie between meningeal layer and periosteal layer (extradural hemorrhage)

Weakest part of skull….middle meningeal artery runs beneath it….

risk of extradural haematoma

Internal Carotid Artery

• Begins at level of upper border of thyroid cartilage

• Ascends within carotid sheath with IJV and Vagus n

• Passes deep to parotid gland• Branches

– No branches in the neck– Ophthalmic artery– Posterior communicating artery– Anterior cerebral artery– Middle cerebral artery

Ophthalmic Artery

• Arises from ICA as it leaves cavernous sinus

• Passes through orbital cavity to optic canal

• Gives off central artery of retina– Enters optic nerve to enter eyeball– End artery– Only blood supply to retina

Posterior Communicating Artery

• Runs backward to join posterior cerebral artery

Anterior Cerebral Artery

• Terminal branch of ICA• Passes forward

between cerebral hemispheres

• Winds around corpus callosum

• Supply medial and superolateral surfaces of cerebral hemispheres

• Joined to artery of opposite side by anterior communicating artery

Middle Cerebral Artery• Largest terminal branch of ICA• Runs laterally in lateral cerebral sulcus• Supplies lateral surface of cerebral hemisphere

except – narrow strip along superolateral margin (supplied by

anterior cerebral a)– Occipital pole and inferolateral surface of hemisphere

(posterior cerebral a)• Supplies all motor area of cerebral cortex except leg

area• Gives off central branches that supply masses of

gray matter and the internal capsule

Subclavian Arteries

• Right subclavian artery– Arises from brachiocephalic behind R

sternoclavicular joint– Arches upward and laterally over pleura

and scalenus anterior and medius muscles– Becomes axillary artery at outer border of

first rib

Subclavian Arteries

• Left Subclavian Artery– Arises from the arch of aorta– Ascends to root of neck then arches

laterally

• Scalenus anterior muscle used to divide the subclavian artery into 3 parts

First Part of the Subclavian Artery

• Extends from the origin of subclavian a to medial border of scalenus anterior muscle

• Branches– Vertebral a– Thyrocervical trunk– Internal thoracic a

Vertebral Artery• Ascends through foramina of

transverse processes of C1-C6

• Passes medially above posterior arch of atlas then through foramen magnum into the skull

• Joins vessel from the opposite side to form basilar artery on the anterior surface of medulla

• Basilar artery– Ascends on the groove

anterior to the pons– Gives off branches to pons,

cerebellum, internal ear– Divides into 2 posterior

cerebral arteries

Vertebral Artery

• Posterior Cerebral a– Curves laterally and

backward around the midbrain

– Cortical branches supply inferolateral surfaces of temporal lobe and visual cortex on lateral and medial surfaces of occipital lobe

Thyrocervical TrunkShort trunk that gives off 3 terminal

branches• Inferior thyroid artery

– Ascends to reach posterior surface of thyroid gland

– Closely related to recurrent laryngeal n

– supplies thyroid and inferior parathyroid glands

• Superficial cervical artery– Runs laterally over phrenic nerve

and crosses brachial plexus• Suprascapular artery

– Follows suprascapular n into supraspinous fossa of scapula

– Takes part in anastomosis around scapula

Internal Thoracic Artery

• Enters thorax behind first costal cartilage and in front of pleura

• Descends vertically one fingerbreadth lateral to the sternum

• Divides into superior epigastric and musculophrenic aa in the 6th ICS

Second Part of Subclavian Artery

• Lies behind scalenus anterior muscle

• Branches– Costocervical trunk

• Runs backward over dome of pleura

• Divides into…– Superior intercostal a

» Supplies 1st and 2nd ICS

– Deep cervical a» Supplies deep

muscles of neck

Third Part of Subclavian Artery

• From lateral border of scalenus anterior m across posterior triangle of neck to lateral border of 1st rib

• Surrounded by axillary sheath of fascia with nerves of brachial plexus

• Branches– Usually no branches– Occasionally, superficial cervical aa, scapular aa

or both arise

Veins of the Head and Neck

• Divided into– Veins of the brain, venous sinuses, diploic

veins and emissary veins– Veins of scalp, face and neck

Veins of the Brain

• Thin-walled• Valveless• Cerebral veins, cerebellar veins and

veins of brain stem• Drain into neighboring venous sinuses

Venous Sinuses

• Situated between periosteal and meningeal layers of dura mater

• With thick fibrous walls• Valveless• Receive tributaries from

brain, skull bones, orbit and internal ear

Venous Sinuses

• Superior Sagittal Sinus– Lies in upper fixed border

of falx cerebri– Runs backward becomes

continuous with right transverse sinus

– Communicates on each side with venous lacunae

– Numerous arachnoid villi and granulations project into the lacunae

Venous Sinuses

• Inferior Sagittal Sinus– Lies in lower free margin of falx cerebri– Runs backward and joins the great cerebral vein

to form straight sinus• Straight Sinus

– Lies at junction of falx cerebri and tentorium cerebelli

– Formed by union of inferior sagittal sinus and great cerebral vein

– Drains into left tranverse sinus

Venous Sinuses

• Transverse Sinuses– R transverse sinus

begins as continuation of superior sagittal s

– Left transverse continuation of straight sinus

– End on each side by becoming sigmoid sinus

Venous Sinuses

• Sigmoid Sinuses– Direct continuation of

the transverse sinuses

– Each curves downward behind the mastoid antrum

– Leaves skull through jugular foramen to become IJV

Venous Sinuses

• Occipital Sinus– Lies in the attached

margin of falx cerebelli

– Communicates with vertebral veins through foramen magnum and with transverse sinuses

Venous Sinuses

• Cavernous sinuses– Each cavernous

sinus lies on lateral side of the body of sphenoid bone

– Receives inferior ophthalmic v and central v of retina anteriorly

– Drains posteriorly into transverse sinus through superior petrosal sinus

Important Structures Associated with the Cavernous Sinuses

• ICA and CN6 travel through it

• CN3 and CN4, ophthalmic and maxillary divisions of CN5 laterally

Dangerous Area of the Face• Triangular area

bounded by root of nose and angles of mouth

• Venous drainage enters angular vein (facial vein) at medial angle of eye

• Communicates with cavernous sinus via superior ophthalmic v

• Infections may lead to cavernous sinus thrombosis

Venous Sinuses

• Superior and Inferior Petrosal Sinuses– Run along the upper

and lower border of the petrous part of the temporal bone

• Diploic Veins– Occupy channels within

bones of the vault of the skull

• Emissary Veins– Valveless veins that pass

through skull bones– Connect veins of scalp to

venous sinuses– Route for spread of

infection

Veins of the Face and Neck• Facial Vein

– Formed at the medial angle of the eye by union of supraorbital and supratrochlear vv

– Connected through ophthalmic veins with the cavernous sinus

– Descends down with facial artery, passes lateral to the mouth

– Crosses the mandible– Joined by

retromandibular v and drains into IJV

Veins of the Face and Neck

• Superficial Temporal Vein– Formed on the side

of the scalp– Follows superficial

temporal a and auriculotemporal n

– Enters parotid gland– Joins maxillary v to

form the retromandibular v

Veins of the Face and Neck

• Maxillary Vein– Formed in the

infratemporal fossa from pterygoid venous plexus

– Joins the superficial temporal v to form the retromandibular v

Veins of the Face and Neck

• Retromandibular Vein– Formed by the union of

the superficial temporal and maxillary vv

– On leaving parotid gland, divides into anterior and posterior branch

– Anterior joins facial v– Posterior joins posterior

auricular v to form EJV

Veins of the Face and Neck

• External Jugular Vein– Formed behind the angle

of the jaw– Union of posterior

auricular v and retromandibular v

– Descends across SCM muscle and beneath platysma muscle

– Drains into subclavian v behind the middle 3rd of clavicle

Tributaries of EJV

• Posterior external jugular vein from the back of the scalp

• Superficial cervical vein from skin and fascia over posterior triangle

• Suprascapular vein from suprascapular fossa

• Anterior jugular vein

Veins of the Face and Neck

• Anterior Jugular Vein– Descends in the neck

close to the midline– Joined to opposite vein

by jugular arch above the sternum

– Anterior jugular v joins external jugular v deep to the SCM muscle

Veins of the Face and Neck• Internal Jugular Vein

– Large vein that drains blood from the brain, face, scalp and neck

– Starts as continuation of sigmoid venous sinus– Leaves the skull through jugular foramen– Descends through neck in the carotid sheath– Lateral to the vagus n and internal and common

carotid aa– Ends by joining subclavian v to form

brachiocephalic v behind medial end of clavicle– Closely related to deep cervical lymph nodes

throughout its course

Tributaries of IJV

• Inferior petrosal sinus

• Facial vein• Pharyngeal veins• Lingual vein• Superior thyroid vein• Middle thyroid vein

Subclavian Vein

• Continuation of axillary v at the outer border of 1st rib

• Joins IJV to form brachiocephalic v

• Receives external jugular v

• Receives thoracic duct on the left and right lymphatic duct on the right

Lymphatic Drainage of the Head and Neck

• Lymph nodes are arranged in 2 groups–Regional group

• surrounds neck below chin like a collar–Deep vertical group

• embedded in carotid sheath

Lymphatic Drainage of Head and Neck

• Regional Lymph Nodes– Occipital nodes

• Apex of posterior triangle

• Drains back of scalp– Mastoid nodes

• Over mastoid process• Scalp above ear, auricle

and external auditory meatus

– Parotid nodes• On or within parotid

gland• Scalp above parotid,

eyelids, auricle, external auditory meatus

Lymphatic Drainage of Head and Neck

• Regional Lymph Nodes– Buccal nodes

• On buccinator muscle• Face and anterior part of scalp• Pass lymph to submandibular nodes

– Submandibular nodes• Superficial to submandibular gland below body of

mandible• Front of scalp, nose, cheek, upper and lower lip (except

central part of lower lip); frontal, maxillary and ethmoid sinuses; upper and lower teeth (except lower incisors); anterior 2/3 of tongue (except tip); floor of the mouth, vestibule, gums

Lymphatic Drainage of Head and Neck

• Regional Lymph Nodes– Submental nodes

• Submental triangle just below chin• Tip of tongue, floor of anterior part of the mouth, lower

incisors, central part of lower lip, skin over chin– Anterior cervical nodes

• Along course of AJV• Skin of front of the neck

– Superficial cervical nodes• Along EJV• Skin over angle of jaw, lower part of parotid and ear lobe

Lymphatic Drainage of Head and Neck

• Regional Lymph Nodes– Retropharyngeal nodes

• Between pharynx and vertebral column• Nasopharynx, auditory canal, vertebral column

– Laryngeal nodes• In front• Larynx

– Tracheal (paratracheal) nodes• Alongside trachea• Trachea and thyroid gland

Lymphatic Drainage of Head and Neck

• Deep Cervical Lymph Nodes– Arranged in vertical chain along course of IJV within carotid

sheath– Receive lymph from all regional nodes– Efferent lymph vessels from deep cervical nodes join to form

jugular trunk which drains into thoracic duct or right lymphatic duct

• Jugulodigastric nodes– Behind angle of jaws– Drains the tonsil

• Jugulo-omohyoid node– Approximately halfway down the neck– Drainage of the tongue

Eye Movements, the Extrinsic Muscles

Eye Movements, the Extrinsic Muscles

Extrinsic Eye Muscles

Muscle Movement Test Nerve Supply

Origin Insertion

Medial Rectus

Medial Lateral Occulomotor (III)

Common Tendinous

Ring

Sclera, anterior half

of eye

Lateral Rectus

Lateral Medial Abducens (VI)

(5mm behind corneal margin)

Superior Rectus

Superior and medial

(adduction)

Lat and dwn Occulomotor (III)

Inferior Rectus

Inferior and medial

(adduction)

Lat and up Occulomotor (III)

Superior Oblique

Inferior and lateral

(abduction)

Med and dwn Trochlear (IV)

Body of sphenoid

Post/Superior Quadrant via

trochlear

Inferior Oblique

Superior and lateral

(abduction)

Med and dwn Occulomotor (III)

Orbital surface of maxilla

Post/inferior quadrant

Muscle Movement Nerve Supply Origin Insertion

Medial Rectus

Medial Occulomotor (III) Common Tendinous

Ring

Sclera, anterior half of eye (5mm behind corneal

margin)

Lateral Rectus

Lateral Abducens (VI)

Superior Rectus

Superior and medial

Occulomotor (III)

Inferior Rectus

Inferior and medial

Occulomotor (III)

Superior Oblique

Inferior and lateral

Trochlear (IV) Body of sphenoid

Post/Superior Quadrant via

trochlear

Inferior Oblique

Superior and lateral

Occulomotor (III) Orbital surface of

maxilla

Post/inferior quadrant

Extrinsic Eye Muscles

Isolated Muscle Actions

Testing Eye Movements

Third nerve palsy

Accompanied by double vision (PS fibres run with III)

Parts of the Ear

• External ear• Middle ear• Inner ear

External Ear

• Auricle (pinna)– Elastic cartilage– Skin

• External Auditory Meatus– S-shaped canal– Inner bony, outer

cartilaginous– Ceruminous glands

Middle Ear

Tympanic Cavity• Lateral - tympanic membrane• Medial - lateral wall of internal ear

– Promontory– Fenestra vestibuli– Fenestra cochlea– Facial canal prominence

• Anterior - eustachian tube• Posterior - mastoid antrum to mastoid air cells• Roof - tegmen tympani to cranial cavity• Floor - adjacent to jugular bulb

Middle Ear

Contents• Auditory ossicles

– Malleus– Incus– Stapes

• Muscles– Tensor tympani (CN V)– Stapedius (CN VII)

Internal Ear

Bony (osseus) Labyrinth • Contains perilymph

– Transudate from blood vessels– Fluid spaces around CN VII and possibly CSF

• Composed of– Vestibule– Semicircular canals– Cochlea

Bony Labyrinth of the Internal Ear

• Semicircular canals– Superior (anterior)– Lateral (horizontal)– posterior

Bony Labyrinth of the Internal Ear

Cochlea• 2 1/2 turns around mediolus• Scala vestibuli and scala

tympani connect at helicotrema

• Oval window opens into scala vestibuli

• Round window closed by secondary tympanic membrane, expands with excessive movement of perilymph in scala tympani

Internal Ear

Membranous Labyrinth• Contains endolymph

– Secreted at stria vascularis• Composed of

– Utricle and saccule– Semicircular ducts– Cochlear duct– Vestibular membrane

Membranous Labyrinth of the Inner Ear

– Utricle and saccule (vestibule) • Maculae

– sensory area of utricle and saccule

– macula utriculi, macula sacculi

– receptors for static equilibrium

Membranous Labyrinth of the Inner Ear

• Semicircular ducts (canals)– Cristae

ampullares• sensory area of

semicircular ducts at ampullae

• receptors for kinetic equilibrium

Membranous Labyrinth of the Inner Ear

• Cochlear duct or scala media (cochlea)– Organ of Corti

• sensory area of cochlear duct

• lies on basilar membrane

• receptor for hearing

Membranous Labyrinth of the Inner Ear

• Vestibular (Reissner’s membrane)– Separates scala

vestibuli from scala media (or cochlear duct)