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Head & Neck Anatomy - Complete Viva Q&A

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SECTION 1: TRIANGLES OF THE NECK

• Lateral: Anterior border of sternocleidomastoid (SCM)
• Superior: Inferior border of mandible
• Medial: Midline of neck
• Gray's Anatomy for Students

1. Submandibular triangle - bounded by inferior border of mandible above; anterior and posterior bellies of digastric below
2. Submental triangle - bounded by body of hyoid inferiorly, anterior belly of digastric on each side, mandibular symphysis superiorly (single, unpaired)
3. Muscular triangle - bounded by hyoid superiorly, superior belly of omohyoid + anterior border of SCM laterally, midline
4. Carotid triangle - bounded by superior belly of omohyoid anteroinferiorly, stylohyoid + posterior belly of digastric superiorly, anterior border of SCM posteriorly

• Anteriorly: Posterior edge of SCM
• Posteriorly: Anterior edge of trapezius
• Base: Middle one-third of clavicle
• Apex: Occipital bone, posterior to mastoid process
• Roof: Investing layer of cervical fascia
• Floor: Prevertebral fascia covering splenius capitis, levator scapulae, and scalene muscles (anterior, middle, posterior)

• Occipital triangle (larger, superior)
• Omoclavicular (subclavian) triangle (smaller, inferior)

• Innervated by ansa cervicalis (anterior rami C1-C3)
• Action: depresses the hyoid bone
• It has two bellies connected by a tendon anchored by a fascial sling to the clavicle

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SECTION 2: SUPRAHYOID & INFRAHYOID MUSCLES

• All suprahyoid muscles raise the hyoid (as in swallowing)

• Omohyoid, Sternohyoid, Thyrohyoid, Sternothyroid
• All innervated by ansa cervicalis (C1-C3), except thyrohyoid which is supplied by C1 via XII
• Action: depress the hyoid/larynx after swallowing

• Superior root (descendens hypoglossi): fibers from C1 running with XII
• Inferior root (descendens cervicalis): from C2-C3
• It supplies all infrahyoid muscles except thyrohyoid

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SECTION 3: STERNOCLEIDOMASTOID (SCM)

• Origin: Two heads - sternal head (manubrium sterni) and clavicular head (medial third of clavicle)
• Insertion: Mastoid process and superior nuchal line of occipital bone

• Motor: Accessory nerve (CN XI)
• Sensory: C2, C3 (via cervical plexus)
• Action: Unilateral - tilts head to same side, rotates chin to opposite side; Bilateral - flexes neck, raises chin

• Injury to SCM in birth (e.g., difficult delivery) can cause torticollis (wry neck) - fibrosis of SCM tilts head to same side
• Erb's point: the point on the posterior border of SCM where five nerves emerge - great auricular, lesser occipital, transverse cervical, supraclavicular, and accessory nerve

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SECTION 4: THYROID GLAND

• Consists of two lateral lobes connected by an isthmus
• Isthmus crosses 2nd and 3rd tracheal cartilages anteriorly
• Lateral lobes cover anterolateral surfaces of trachea, cricoid, and lower thyroid cartilage
• Lies deep to sternohyoid, sternothyroid, omohyoid muscles (strap muscles)
• Surrounded by pretracheal fascia

• Superior thyroid artery: first branch of external carotid artery; descends along lateral margin of thyrohyoid muscle
• Inferior thyroid artery: branch of thyrocervical trunk (from 1st part of subclavian artery); passes posterior to carotid sheath
• Thyroid ima artery (occasional): arises from brachiocephalic trunk or aortic arch; ascends on anterior trachea

• Superior thyroid vein → internal jugular vein
• Middle thyroid vein → internal jugular vein
• Inferior thyroid veins (paired) → right and left brachiocephalic veins, respectively

• The RLN ascends in the tracheo-oesophageal groove, passes deep to the posteromedial surface of each lateral lobe, and enters the larynx below the inferior constrictor
• The RLN closely relates to the inferior thyroid artery at the gland and may pass through the Berry's ligament (thickening of pretracheal fascia attaching thyroid to trachea/cricoid)
• Surgical handling of the inferior pole or ligation of inferior thyroid artery risks RLN injury causing hoarseness (unilateral) or respiratory obstruction (bilateral)

• Develops from median outgrowth of the floor of the pharynx, near the base of the tongue
• Site of origin marked by the foramen caecum on the tongue
• Descends via the thyroglossal duct to its final position
• Remnants → thyroglossal cyst (along midline) or lingual thyroid
• A pyramidal lobe extends upward from the isthmus along the path of descent

• Superior parathyroids: from 4th pharyngeal pouch
• Inferior parathyroids: from 3rd pharyngeal pouch (same pouch as thymus, hence more variable position - can be anywhere from carotid bifurcation to mediastinum)

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SECTION 5: PAROTID GLAND

• Largest of three pairs of salivary glands (parotid, submandibular, sublingual)
• Located anterior and inferior to the lower half of the ear; extends from zygomatic arch to lower border of mandible; posteriorly covers anterior part of SCM; anteriorly extends halfway across masseter

1. Facial nerve [VII] - exits stylomastoid foramen → enters parotid → divides into upper and lower trunks → five terminal branches emerge (Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical - "Ten Zebras Bit My Cat")
2. External carotid artery - gives posterior auricular artery, then divides into maxillary + superficial temporal arteries within/deep to gland
3. Retromandibular vein - formed within gland, divides into anterior and posterior divisions

• The Stensen's duct (parotid duct) leaves the anterior edge of gland midway between zygomatic arch and corner of mouth
• Crosses the face, turns deeply at the medial border of masseter, pierces buccinator, opens into oral cavity opposite the upper 2nd molar tooth

• Auriculotemporal nerve (branch of V3) carries parasympathetic secretomotor fibers
• The preganglionic fibers originate in the inferior salivatory nucleus via CN IX (glossopharyngeal)
• They synapse in the otic ganglion (located medial to V3 just below foramen ovale)
• Postganglionic fibers travel via auriculotemporal nerve to parotid

• Occurs after parotid surgery or injury
• Auriculotemporal nerve fibers (parasympathetic/secretomotor) aberrantly regenerate to sweat glands of overlying skin
• Results in gustatory sweating - facial sweating and flushing while eating (instead of salivation)

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SECTION 6: PHARYNX & LARYNX

• Nasopharynx: from skull base to soft palate; contains pharyngeal tonsil (adenoids), opening of Eustachian tube
• Oropharynx: from soft palate to epiglottis; contains palatine tonsils, posterior tongue (vallecula)
• Laryngopharynx (hypopharynx): from epiglottis to lower border of cricoid; includes pyriform fossae on either side of larynx; continuous with oesophagus

• The aryepiglottic folds form the inlet of the larynx
• Vestibular folds (false cords) and vocal folds (true cords) are above and below the ventricle respectively
• Reinke's space: subepithelial potential space in the vocal folds where edema accumulates (Reinke's edema from smoking)

• Internal branch of superior laryngeal nerve (SLN): sensory to larynx above glottis; also taste above epiglottis
• External branch of SLN: motor to cricothyroid muscle only
• Recurrent laryngeal nerve (RLN): all other intrinsic laryngeal muscles; sensory below glottis
• Both SLN and RLN are branches of the vagus nerve (CN X)

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SECTION 7: CRANIAL NERVES IN HEAD & NECK

• Origin: lower pontine junction at the cerebellopontine angle
• Enters internal acoustic meatus → runs in facial canal of petrous temporal bone → geniculate ganglion (sensation - taste anterior 2/3 tongue)
• Gives branches in petrous bone:
  • Greater petrosal nerve (to pterygopalatine ganglion - lacrimal/nasal/palatal glands)
  • Nerve to stapedius (dampens loud sounds)
  • Chorda tympani (taste anterior 2/3 tongue + secretomotor to submandibular/sublingual glands via lingual nerve to submandibular ganglion)
• Exits stylomastoid foramen → enters parotid gland → five terminal branches

• Exits jugular foramen
• Superior ganglion (general somatic afferent from ear/meninges)
• Inferior (nodose) ganglion (visceral afferent - taste from epiglottis, GI viscera)
• Branches in neck:
  • Pharyngeal branch (with IX and sympathetics forms pharyngeal plexus - motor to all pharyngeal muscles except stylopharyngeus)
  • Superior laryngeal nerve (internal sensory + external motor to cricothyroid)
  • Recurrent laryngeal nerve (right loops under subclavian artery; left loops under arch of aorta)
  • Cardiac branches

• Motor: stylopharyngeus only (elevates pharynx/larynx during swallowing)
• Sensory: posterior 1/3 tongue, pharynx, middle ear (Jacobson's nerve - tympanic plexus)
• Taste: posterior 1/3 tongue
• Parasympathetic: inferior salivatory nucleus → lesser petrosal nerve → otic ganglion → auriculotemporal nerve → parotid gland
• Gag reflex: afferent limb is CN IX, efferent limb is CN X
• Glossopharyngeal neuralgia: pain in throat/ear on swallowing

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SECTION 8: CERVICAL FASCIA

1. Investing (superficial) layer: Surrounds the entire neck; encloses SCM and trapezius; splits to enclose parotid and submandibular glands; attached to hyoid, mandible, zygomatic arch, mastoid, superior nuchal line
2. Pretracheal fascia: Encloses thyroid gland, trachea, oesophagus; blends with pericardium inferiorly - allows spread of infection to mediastinum
3. Prevertebral fascia: Covers prevertebral muscles; forms the "floor" of posterior triangle; extends laterally as the axillary sheath
4. Carotid sheath: Contains internal/common carotid artery, internal jugular vein, vagus nerve (CN X); blends with all three layers

• Infection can track between fascial layers:
  • Retropharyngeal space (between buccopharyngeal/pretracheal and prevertebral fascia) → "danger space" → posterior mediastinum
  • Pretracheal space → anterior mediastinum
  • Understanding these planes guides surgical drainage of deep neck infections

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SECTION 9: BLOOD VESSELS

1. Superior thyroid artery (first branch, descends)
2. Ascending pharyngeal artery (medial, only branch from medial surface)
3. Lingual artery
4. Facial artery
5. Occipital artery
6. Posterior auricular artery
7. Maxillary artery (terminal)
8. Superficial temporal artery (terminal)

• Common carotid artery (medial) / Internal carotid artery
• Internal jugular vein (lateral)
• Vagus nerve (CN X) - between and posterior to artery and vein
• Deep cervical lymph nodes along the internal jugular vein (note: these are outside the sheath but closely related)

• Carotid sinus: Dilatation at the bifurcation of common carotid (or origin of ICA); a baroreceptor for blood pressure; innervated by CN IX (Hering's nerve)
• Carotid body: Small chemoreceptor organ at the carotid bifurcation; responds to O2, CO2, pH changes; innervated by CN IX and X
• Pressure on carotid sinus → bradycardia, hypotension (carotid sinus syncope)

• Branches of thyrocervical trunk:
  • Inferior thyroid artery (gives ascending cervical and muscular branches)
  • Suprascapular artery
  • Transverse cervical artery (superficial cervical + dorsal scapular)

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SECTION 10: SCALP, SKULL, AND MENINGES

• S - Skin
• C - subcutaneous Connective tissue (dense, contains vessels/nerves - bleeds profusely when cut)
• A - Aponeurosis (epicranial - galea aponeurotica)
• L - Loose areolar tissue ("dangerous layer" - infection/blood spreads; emissary veins connect superficial to intracranial veins)
• P - Pericranium (periosteum of skull)

• The loose areolar layer (layer 4) contains emissary veins that communicate with diploic veins within skull and dural venous sinuses inside the skull
• Infection in this layer can spread intracranially to cause meningitis or venous sinus thrombosis
• Blood can accumulate here in a "subgaleal hematoma" which can spread widely (no attachment barriers)

• Superior sagittal sinus (in upper margin of falx cerebri → confluens sinuum)
• Inferior sagittal sinus (lower margin of falx → straight sinus)
• Straight sinus (at junction of falx and tentorium → confluens sinuum)
• Transverse sinuses (from confluens → sigmoid sinuses → IJV)
• Cavernous sinuses (either side of sella turcica; connected by intercavernous sinuses)
• Superior and inferior petrosal sinuses
• Occipital sinus

• Within the sinus: internal carotid artery + CN VI (abducens)
• In lateral wall (from superior to inferior): CN III (oculomotor), CN IV (trochlear), CN V1 (ophthalmic), CN V2 (maxillary)
• Mnemonic: "O TOM CAT" (Oculomotor, Trochlear, Ophthalmic, Maxillary - Carotid Abducens Traversing)

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SECTION 11: ORBIT & EYE

• When the eye is adducted (looking in), the superior oblique depresses the eye
• When the eye is abducted (looking out), it intorts the eye
• CN IV palsy: eye is extorted and the person complains of vertical diplopia, especially going downstairs (requires depression of adducted eye)
• Patient tilts head to opposite side (to compensate for extorsion - Bielschowsky's test)

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SECTION 12: MANDIBLE, TMJ & TEETH

• A synovial joint between the condyle of mandible and mandibular fossa + articular tubercle of temporal bone
• Divided into upper and lower compartments by an articular disc (fibrocartilage)
• Upper compartment: gliding movement (jaw protrusion/retrusion)
• Lower compartment: hinge movement (mouth opening/closing - rotation)
• Movements: depression, elevation, protrusion, retrusion, lateral (grinding)
• Muscles of mastication: temporalis, masseter, medial pterygoid, lateral pterygoid - all supplied by CN V3 (mandibular nerve)

• Closing: Temporalis (elevation + retrusion), Masseter (elevation), Medial pterygoid (elevation + protrusion)
• Opening/Depression: Lateral pterygoid (protrudes condyle - opens jaw), digastric, geniohyoid, mylohyoid
• All muscles of mastication supplied by mandibular nerve (V3)

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SECTION 13: TONGUE

• All intrinsic muscles (superior/inferior longitudinal, transverse, vertical) and all extrinsic muscles (genioglossus, hyoglossus, styloglossus, palatoglossus) are supplied by CN XII (hypoglossal nerve)
• Exception: Palatoglossus is supplied by the vagus nerve (CN X) via the pharyngeal plexus

• Anterior 2/3:
  • General sensation: lingual nerve (V3)
  • Taste: chorda tympani (VII) via lingual nerve
• Posterior 1/3:
  • Both general sensation and taste: CN IX (glossopharyngeal nerve)
• Epiglottis and extreme posterior tongue: CN X (vagus) - internal branch of SLN

• Tongue deviates to the side of the lesion on protrusion
• The intact genioglossus on the normal side pushes tongue to the weak side
• LMN lesion: wasting and fasciculations of tongue on affected side

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SECTION 14: NOSE & PARANASAL SINUSES

• The maxillary sinus drains at its superomedial wall - poorest dependent drainage, hence prone to infection

• Olfactory nerve (CN I): smell - via cribriform plate to roof of nasal cavity
• Ophthalmic division (V1): anterior ethmoidal nerve (anterosuperior septum and lateral wall)
• Maxillary division (V2): nasopalatine nerve (posterior septum), posterior lateral nasal branches (via pterygopalatine ganglion)
• Parasympathetics: from pterygopalatine ganglion (via CN VII) → vasodilation, secretion

• Anteroinferior part of the nasal septum where five arteries anastomose:
  1. Anterior ethmoidal artery (from ophthalmic artery - ICA)
  2. Posterior ethmoidal artery (from ophthalmic artery - ICA)
  3. Sphenopalatine artery (from maxillary artery - ECA)
  4. Greater palatine artery (from maxillary artery - ECA)
  5. Superior labial branch of facial artery (ECA)
• Site of 90% of anterior epistaxis

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SECTION 15: EAR

• External ear: Pinna (auricle) + external auditory meatus + tympanic membrane
• Middle ear (tympanic cavity): ossicles (malleus, incus, stapes), Eustachian tube, oval and round windows, facial nerve in its canal
• Inner ear: Cochlea (hearing), semicircular canals + utricle + saccule (balance)

• Outer surface: auriculotemporal nerve (V3) and auricular branch of vagus (Arnold's nerve - CN X)
• Inner surface: tympanic plexus (CN IX - Jacobson's nerve)
• This is why cardiac disease, herpes zoster oticus (Ramsay Hunt syndrome), and irritation of the ear can cause referred pain to the throat/face and vice versa

• Roof (tegmental wall): tegmen tympani (thin plate of petrous temporal)
• Floor (jugular wall): jugular bulb of IJV
• Medial wall (labyrinthine): oval window (stapes), round window, promontory (cochlea bulge), facial nerve canal
• Lateral wall (membranous): tympanic membrane
• Anterior wall (carotid): internal carotid artery, Eustachian tube
• Posterior wall (mastoid): aditus to mastoid antrum, facial nerve

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SECTION 16: HIGH-YIELD QUICK FACTS

• Pharyngeal tonsil (adenoids) - nasopharynx (superiorly)
• Tubal tonsils (near Eustachian tube opening)
• Palatine tonsils (between palatoglossal and palatopharyngeal arches)
• Lingual tonsil (base of tongue)
• Acts as first line of immune defense against inhaled/ingested antigens

• Recesses on either side of the laryngeal inlet in the hypopharynx
• The internal branch of superior laryngeal nerve lies in the mucosa of the pyriform fossa
• Foreign bodies often lodge here
• Endoscopic topical anesthesia injected into piriform fossa anesthetizes the larynx

• Located between the alar fascia (anterior part of prevertebral fascia) and the prevertebral fascia proper
• Extends from skull base to the posterior mediastinum (as far as the diaphragm)
• Infection can spread from deep neck spaces to mediastinum via this path - cause of descending necrotizing mediastinitis

• A condensation of pretracheal fascia attaching the posterior capsule of each thyroid lobe to the cricoid cartilage and upper tracheal rings
• The recurrent laryngeal nerve is intimately related to it (may pass through or behind it)
• Critical landmark in thyroid surgery

• Level I: Submental (Ia) + Submandibular (Ib)
• Level II: Upper jugular (IIa anterior, IIb posterior to accessory nerve)
• Level III: Middle jugular
• Level IV: Lower jugular
• Level V: Posterior triangle (Va + Vb)
• Level VI: Central compartment (prelaryngeal/Delphian, pretracheal, paratracheal)
• Level VII: Superior mediastinal nodes

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