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Head & neck

Third module — usually after the trunk and before the limbs

Head and neck is the densest module of gross anatomy: small structures, many of them nerves, packed around bone you can't dissect through. The organizing idea is the cranial nerves — learn where each one leaves the skull, what it moves, what it feels, and which parasympathetic ganglion it borrows, and most of the region files itself. The written exam lives at foramina, nerve lesions (which muscle fails, which way the eye or tongue deviates), and the carotid and jugular systems; the practical adds the neck triangles, the larynx, and the facial muscles. It is also the region where anatomy turns most directly into a physical exam: every cranial-nerve test you will perform in clinic is this module.

On the PANCE this region feeds:Eyes/Ears/Nose/Throat · 6%Neurology · 7%Endocrine · 6%
High-Yield Pearl

Ask three questions of any head and neck structure — which cranial nerve supplies it, which hole that nerve leaves the skull through, and which pharyngeal arch it came from — and you can predict its innervation, its lesion, and its neighbors.

Practice it
Active recall over the structure list below — flip and claim, match the pairs, label from a bank, or fill in the diagram.

Every structure on the practical list, one card at a time — the name up front, the identifying relationship on the flip. Claim each card honestly and the deck learns what to lead with next time. Progress lives in this browser only.

What the written exam asks
Relationships, supply, levels, and what happens when each fails.
  • Cranial fossae and the foramina. Anterior fossa: the cribriform plate (olfactory fibers, CN I). Middle fossa: the optic canal (CN II and the ophthalmic artery), the superior orbital fissure (CN III, IV, V1, VI and the superior ophthalmic vein), foramen rotundum (V2), foramen ovale (V3 and the lesser petrosal nerve), and foramen spinosum (the middle meningeal artery). Posterior fossa: the internal acoustic meatus (CN VII and VIII), the jugular foramen (CN IX, X, XI and the internal jugular vein), the hypoglossal canal (CN XII), and the foramen magnum (the medulla, the vertebral arteries, and the spinal roots of XI). "Standing Room Only" orders the middle-fossa row for V1, V2, V3.
  • Meninges, bleeds, and the dural venous sinuses. Dura (with its falx cerebri and tentorium cerebelli folds), arachnoid, and pia. An EPIDURAL hematoma is arterial — usually the middle meningeal artery torn under the thin pterion — lens-shaped, stopped by the sutures, often with a lucid interval. A SUBDURAL hematoma is venous — bridging veins torn in the elderly or in shaken infants — crescent-shaped and crossing sutures. A subarachnoid hemorrhage is usually a ruptured berry aneurysm: the worst headache of life. Venous blood drains through the dural sinuses (superior sagittal → confluence → transverse → sigmoid → internal jugular vein); the cavernous sinus beside the sella carries the internal carotid artery and CN VI inside it and CN III, IV, V1, and V2 in its lateral wall.
  • The cranial nerves and their parasympathetic ganglia. Four nerves carry the head's parasympathetic outflow, each through a named ganglion: CN III → ciliary ganglion → pupillary sphincter and ciliary muscle; CN VII → pterygopalatine ganglion → lacrimal, nasal, and palatal glands, and CN VII → submandibular ganglion → submandibular and sublingual glands; CN IX → otic ganglion → parotid gland (the fibers ride the auriculotemporal nerve). CN X carries the rest to the thorax and abdomen. Sympathetic fibers reach the head from the superior cervical ganglion along the arteries — which is why a lesion anywhere along that chain gives Horner syndrome (ptosis, miosis, anhidrosis).
  • The face — CN VII moves it, CN V feels it. The muscles of facial expression develop from the second pharyngeal arch and are all supplied by the facial nerve, whose five branches (temporal, zygomatic, buccal, marginal mandibular, cervical) fan out through the parotid gland. Sensation comes from the trigeminal divisions: V1 (forehead, upper lid, nose bridge), V2 (cheek, upper lip), V3 (lower lip, chin, and the jaw except its angle, which is C2–C3). The facial artery crosses the mandible at the anterior border of masseter; the facial vein connects through the ophthalmic veins to the cavernous sinus, so infections of the central face ('danger triangle') can spread intracranially.
  • Mastication and the temporomandibular joint. The four muscles of mastication come from the first arch and are supplied by V3: masseter, temporalis, and medial pterygoid close the jaw; the LATERAL pterygoid protrudes the mandible and opens it, pulling the condyle and articular disc forward onto the articular eminence. The TMJ is a synovial joint divided by that disc into upper (gliding) and lower (hinge) compartments. Dislocation is anterior, with the condyle trapped in front of the eminence.
  • The orbit and eye movements. LR6 SO4, the rest 3: the lateral rectus is CN VI, the superior oblique is CN IV, and CN III supplies the medial, superior, and inferior recti, the inferior oblique, and the levator palpebrae superioris. To test a muscle in isolation, move the eye into the position where it is the prime mover: the superior oblique depresses the ADDUCTED eye (looking down and in, as when reading or descending stairs). CN III palsy leaves the eye 'down and out' with ptosis; a compressive lesion (posterior communicating aneurysm, uncal herniation) also dilates the pupil because the parasympathetic fibers ride on the nerve's surface, while a diabetic (ischemic) palsy usually spares it. The pupil is constricted by CN III parasympathetics and dilated by sympathetics; the upper lid is raised by levator (CN III) with help from the smooth superior tarsal muscle (sympathetic).
  • Nasal cavity and paranasal sinuses. Three conchae overhang three meatuses. The frontal, maxillary, and anterior ethmoidal sinuses drain into the middle meatus (via the semilunar hiatus); the posterior ethmoidal cells into the superior meatus; the sphenoid sinus into the sphenoethmoidal recess; and the nasolacrimal duct into the inferior meatus. The maxillary sinus drains through an ostium high on its medial wall, which is why it clears poorly and is the sinus most often infected. Anterior nosebleeds come from Kiesselbach's area on the septum, where branches of the ophthalmic, maxillary, and facial arteries anastomose.
  • Oral cavity, tongue, and salivary glands. All tongue muscles are CN XII except palatoglossus (CN X). A hypoglossal lesion makes the tongue deviate TOWARD the weak side, because the intact genioglossus pushes it over. Anterior two-thirds: general sensation by the lingual nerve (V3) and taste by the chorda tympani (VII) riding with it. Posterior third: both by CN IX. The parotid duct pierces buccinator opposite the upper second molar; the submandibular duct opens beside the lingual frenulum and is crossed by the lingual nerve.
  • Pharynx and swallowing. Three pharyngeal constrictors (superior, middle, inferior) squeeze the bolus down; stylopharyngeus (CN IX) elevates the pharynx; all other pharyngeal and palatal muscles are CN X except tensor veli palatini (V3). The gag reflex runs IX in and X out. Killian's triangle, a weak spot in the inferior constrictor, is where a Zenker diverticulum herniates. The palatine tonsil sits between the palatoglossal and palatopharyngeal arches, with the glossopharyngeal nerve deep to its bed.
  • The larynx. Cartilages: thyroid (the laryngeal prominence), cricoid (the only complete ring, at C6), paired arytenoids, and the epiglottis. Every intrinsic laryngeal muscle is supplied by the recurrent laryngeal nerve EXCEPT cricothyroid, which tenses the folds and is supplied by the external branch of the superior laryngeal nerve. The posterior cricoarytenoid is the ONLY abductor — bilateral recurrent nerve injury can close the airway. Sensation above the vocal folds is the internal laryngeal nerve (the afferent limb of the cough reflex); below them, the recurrent laryngeal. The cricothyroid membrane, between the thyroid and cricoid cartilages, is the emergency surgical airway.
  • The triangles and fascial compartments of the neck. Sternocleidomastoid (CN XI) divides the neck into anterior and posterior triangles. The anterior triangle holds the carotid sheath — common and internal carotid arteries medially, internal jugular vein laterally, vagus nerve posterior between them — plus the thyroid, larynx, and hyoid muscles. The posterior triangle is crossed superficially by the spinal accessory nerve on its way to trapezius (easily cut in lymph-node biopsy) and contains the cervical plexus and the trunks of the brachial plexus emerging between anterior and middle scalene. The phrenic nerve (C3–C5) runs down the anterior surface of anterior scalene; the subclavian VEIN passes in front of that muscle, the subclavian ARTERY behind it.
  • The carotid system and vertebral arteries. The common carotid bifurcates at the upper border of the thyroid cartilage (about C4). The internal carotid gives NO branches in the neck; its origin dilates into the carotid sinus (baroreceptor, CN IX) with the carotid body (chemoreceptor) beside it. The external carotid branches in the neck — superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, then the maxillary and superficial temporal terminal branches — and the maxillary artery gives the middle meningeal. The vertebral arteries, first branches of the subclavians, climb through the transverse foramina of C6–C1 and enter the skull through the foramen magnum to form the basilar artery.
  • Thyroid and parathyroid glands. The thyroid's isthmus crosses tracheal rings 2–4. The superior thyroid artery (first branch of the external carotid) runs with the external laryngeal nerve; the inferior thyroid artery (from the thyrocervical trunk) is intimately related to the recurrent laryngeal nerve in the tracheoesophageal groove — the two nerve injuries of thyroid surgery. The gland descends from the foramen cecum of the tongue, so a thyroglossal duct cyst is a midline mass that moves up when the tongue protrudes. Four parathyroid glands sit on the posterior surface; the inferior pair (from the third pharyngeal pouch, with the thymus) wander most.
What the practical tags · 70 structures
In the order a dissection meets them — each with the one relationship that identifies it. Your lab's study list is the authority; use this to check yours against.
  1. 1Pterion — H-shaped junction of frontal, parietal, temporal, and sphenoid bones over the middle meningeal artery
  2. 2Cribriform plate — the perforated ethmoid carrying olfactory nerve fibers
  3. 3Optic canal — carries CN II and the ophthalmic artery
  4. 4Superior orbital fissure — CN III, IV, V1, VI and the superior ophthalmic vein
  5. 5Foramen rotundum — the maxillary nerve (V2)
  6. 6Foramen ovale — the mandibular nerve (V3)
  7. 7Foramen spinosum — the middle meningeal artery
  8. 8Internal acoustic meatus — the facial and vestibulocochlear nerves
  9. 9Jugular foramen — CN IX, X, XI and the internal jugular vein
  10. 10Hypoglossal canal — CN XII, just above the occipital condyle
  11. 11Foramen magnum — the medulla, the vertebral arteries, and the spinal roots of XI
  12. 12Falx cerebri — the midline dural fold between the hemispheres
  13. 13Tentorium cerebelli — the dural shelf roofing the posterior fossa
  14. 14Superior sagittal sinus — along the falx's attached edge; arachnoid granulations drain into it
  15. 15Cavernous sinus — beside the sella; ICA and CN VI inside, III, IV, V1, V2 in its wall
  16. 16Middle meningeal artery — grooves the inner skull beneath the pterion
  17. 17Orbicularis oculi — closes the eyelids (CN VII)
  18. 18Orbicularis oris — purses and closes the lips (CN VII)
  19. 19Buccinator — the cheek muscle the parotid duct pierces
  20. 20Parotid gland — largest salivary gland; the facial nerve branches inside it
  21. 21Parotid duct — crosses masseter and opens opposite the upper second molar
  22. 22Facial nerve branches — temporal, zygomatic, buccal, marginal mandibular, cervical
  23. 23Masseter — elevates the mandible; bulges when the teeth clench
  24. 24Temporalis — fan-shaped elevator inserting on the coronoid process
  25. 25Lateral pterygoid — the only muscle of mastication that opens the jaw
  26. 26Medial pterygoid — elevator forming a sling with masseter around the ramus
  27. 27Facial artery — crosses the mandible at masseter's anterior border
  28. 28Superficial temporal artery — pulse in front of the ear; terminal branch of the external carotid
  29. 29Maxillary artery — deep terminal branch of the external carotid; gives the middle meningeal
  30. 30Levator palpebrae superioris — raises the upper lid (CN III)
  31. 31Superior oblique — CN IV; its tendon turns through the trochlea
  32. 32Lateral rectus — CN VI; abducts the eye
  33. 33Medial rectus — CN III; adducts the eye
  34. 34Ciliary ganglion — parasympathetic relay behind the eye for CN III
  35. 35Nasal conchae — superior, middle, and inferior scrolls, each over its meatus
  36. 36Middle meatus — frontal, maxillary, and anterior ethmoidal sinuses open here
  37. 37Inferior meatus — the nasolacrimal duct opens here
  38. 38Maxillary sinus — the largest paranasal sinus, draining through a high ostium
  39. 39Sphenoid sinus — below the sella; the transsphenoidal route to the pituitary
  40. 40Kiesselbach area — the anterior septal plexus where most nosebleeds start
  41. 41Genioglossus — protrudes the tongue (CN XII)
  42. 42Lingual nerve — V3 sensation to the anterior tongue, carrying chorda tympani fibers
  43. 43Submandibular duct — opens beside the frenulum; crossed by the lingual nerve
  44. 44Submandibular gland — wraps around the posterior border of mylohyoid
  45. 45Palatine tonsil — between the palatoglossal and palatopharyngeal arches
  46. 46Hyoid bone — at C3; anchor for the suprahyoid and infrahyoid muscles
  47. 47Thyroid cartilage — the laryngeal prominence; the carotids bifurcate at its upper border
  48. 48Cricoid cartilage — the only complete laryngeal ring, at C6
  49. 49Cricothyroid membrane — the emergency airway site between the thyroid and cricoid cartilages
  50. 50Cricothyroid muscle — tenses the vocal folds; supplied by the external laryngeal nerve
  51. 51Posterior cricoarytenoid — the only abductor of the vocal folds
  52. 52Epiglottis — elastic flap that tips over the laryngeal inlet in swallowing
  53. 53Vocal folds — the true cords, below the vestibular folds, bounding the rima glottidis
  54. 54Sternocleidomastoid — divides the anterior from the posterior triangle (CN XI)
  55. 55Spinal accessory nerve — crosses the posterior triangle superficially to reach trapezius
  56. 56Carotid sheath — carotid artery, internal jugular vein, and vagus nerve together
  57. 57Carotid sinus — dilation at the internal carotid origin; baroreceptor on CN IX
  58. 58External carotid artery — the carotid that branches in the neck, superior thyroid first
  59. 59Internal jugular vein — lateral in the carotid sheath; a central-line target
  60. 60Vagus nerve — posterior in the sheath, between the artery and the vein
  61. 61Hypoglossal nerve — loops forward across both carotids above the hyoid
  62. 62Ansa cervicalis — C1–C3 loop on the sheath supplying the infrahyoid muscles
  63. 63Anterior scalene — phrenic nerve on its face; subclavian vein in front, artery behind
  64. 64Phrenic nerve — C3–C5, descending on anterior scalene
  65. 65Vertebral artery — first subclavian branch, climbing through the transverse foramina
  66. 66Thyrocervical trunk — subclavian branch giving the inferior thyroid artery
  67. 67Thyroid gland — isthmus over tracheal rings 2–4
  68. 68Superior thyroid artery — first external carotid branch, beside the external laryngeal nerve
  69. 69Parathyroid glands — four small glands on the posterior thyroid
  70. 70Recurrent laryngeal nerve — in the tracheoesophageal groove beside the inferior thyroid artery
What everyone misses
The distinctions that lose points on the practical, year after year.
  • Superior orbital fissure vs optic canal. The optic canal carries only CN II and the ophthalmic artery; everything else entering the orbit (III, IV, V1, VI and the superior ophthalmic vein) uses the superior orbital fissure beside it. On a skull the canal is the round hole in the lesser wing; the fissure is the slit between the wings.
  • The tongue deviates TOWARD the lesion. With a right CN XII lesion, the left genioglossus is unopposed and pushes the protruded tongue to the RIGHT — toward the weak side. The uvula does the opposite: with a right CN X lesion, the intact left palatal muscles pull the uvula to the LEFT, away from the lesion. Students mix the two directions.
  • Cricothyroid is the one exception. Every intrinsic laryngeal muscle is on the recurrent laryngeal nerve except cricothyroid (external laryngeal branch of the superior laryngeal). A thyroidectomy injury to the external branch causes a weak, easily fatigued voice that can't reach high pitches; a recurrent injury causes hoarseness from a paralyzed fold.
  • Epidural is arterial, subdural is venous. Lens-shaped, suture-limited, with a lucid interval → epidural, middle meningeal artery. Crescent-shaped, crossing sutures, in an elderly or alcohol-using patient → subdural, bridging veins. The shape on CT and the vessel are paired; learn them together.
  • Testing the superior oblique. The superior oblique is an intorter and depressor, but it is tested with the eye ADDUCTED and looking down, because that is where it is the prime depressor. A CN IV palsy shows vertical diplopia worst when reading or walking downstairs, and patients tilt the head AWAY from the affected side to compensate.
  • The internal carotid has no neck branches. If a vessel in the carotid triangle gives off branches, it is the external carotid — no matter where it lies. The internal carotid, though usually posterolateral at its origin, is identified by NOT branching until it enters the skull.
  • Spinal accessory nerve in the posterior triangle. It runs superficially, just under the investing fascia, from the posterior border of sternocleidomastoid to trapezius — the one important structure in a triangle students treat as empty. Cutting it during a node biopsy produces a drooping shoulder and difficulty abducting above the horizontal.
  • Pupil-sparing vs pupil-involving CN III palsy. The pupillomotor fibers run on the outside of the nerve, where compression reaches them first and the ischemia of diabetes reaches them last. A 'down and out' eye with a dilated pupil is an aneurysm until proven otherwise; with a normal pupil in a diabetic, it is usually microvascular.
Clinical correlations
Where this region shows up again — in clinical medicine, on rotations, and on the boards.
  • Epidural hematoma. A blow to the side of the head fractures the thin pterion and tears the middle meningeal artery; the patient may be lucid before rapidly deteriorating as the arterial bleed expands. CT shows a biconvex collection that does not cross sutures. It is a neurosurgical emergency — evacuation before uncal herniation compresses CN III (a blown pupil on the same side).
  • Bell's palsy vs a central facial palsy. A lower motor neuron facial nerve lesion (Bell's palsy) paralyzes the WHOLE half of the face, forehead included, and may add loss of taste, hyperacusis, and a dry eye depending on the level. An upper motor neuron lesion (stroke) spares the forehead because the forehead's motor neurons receive input from both hemispheres. Forehead involvement is the discriminator.
  • Horner syndrome. Ptosis (loss of the superior tarsal muscle), miosis, and facial anhidrosis from interruption of the sympathetic chain anywhere from the hypothalamus through the cervical ganglia — a Pancoast tumor at the lung apex, carotid dissection, or a lateral medullary stroke. The ptosis is mild because the levator (CN III) still works.
  • Cavernous sinus thrombosis. A central-face or sinus infection spreads through the valveless facial and ophthalmic veins: fever, proptosis, chemosis, and ophthalmoplegia — CN VI often first, because it lies free in the sinus beside the internal carotid — with V1/V2 sensory loss.
  • Epistaxis. About 90% of nosebleeds arise anteriorly at Kiesselbach's area and stop with firm pressure on the soft nose while leaning forward. Posterior bleeds (from sphenopalatine branches) are heavier, occur in older and hypertensive patients, and often need posterior packing.
  • Thyroidectomy nerve injuries and hypocalcemia. Ligating the inferior thyroid artery risks the recurrent laryngeal nerve (hoarseness; bilateral injury can cause stridor and airway obstruction); ligating the superior thyroid artery risks the external laryngeal nerve (lost high pitch). Removing or devascularizing the parathyroids causes hypocalcemia with perioral tingling, Chvostek and Trousseau signs in the following days.
  • Cricothyrotomy. When the airway can't be secured from above, the cricothyroid membrane is found by sliding a finger down from the laryngeal prominence into the soft notch above the cricoid ring. It is superficial, relatively avascular, and above the thyroid isthmus — the reason it is the emergency site rather than a tracheostomy.
  • Carotid sinus massage and hypersensitivity. Pressure over the carotid bifurcation stimulates the sinus baroreceptors (CN IX afferent, CN X efferent), slowing the heart — used to break some supraventricular tachycardias. In carotid sinus hypersensitivity, a tight collar or a head turn can cause syncope.
  • Thyroglossal duct cyst vs branchial cleft cyst. A MIDLINE neck mass that rises when the tongue protrudes is a thyroglossal duct cyst (the thyroid's path of descent). A LATERAL mass along the anterior border of sternocleidomastoid in a young patient is a branchial (second cleft) cyst. Location is the diagnosis.
  • Trigeminal neuralgia and dental anesthesia. Paroxysmal, electric pain in a V2 or V3 distribution triggered by chewing or touch is trigeminal neuralgia, treated first with carbamazepine. The same nerve anatomy underlies the inferior alveolar block, which also numbs the lower lip and, through the nearby lingual nerve, the tongue.

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