HoyaDocs · HNSS Block 5 · Head & Neck AnatomyUpdated 27 Sep 2026 · Rev 1.0

Lab 3 Exam-Day Review

Cranial Fossae — meninges, dural folds, dural venous sinuses, arteries and the 12 cranial nerves at the skull base.

1. Exam-day rules & top traps 2. Meninges, folds & sinuses 3. Cavernous sinus 4. Arteries 5. Cranial nerves at a glance 6. Eye nerves & palsies 7. Reflexes 8. CN IX · X · XI · XII 9. More comparisons 10. Clinical correlations 11. Self-check questions

1 · Exam-Day Rules & Top Traps

✍️ Wording

Full names for structures (“internal carotid artery,” not “ICA”). Cranial nerves may be written as CN III or oculomotor nerve.
Use the lecture’s modality terms: special sensory (CN I, II, VIII, taste), general sensory, branchial motor.
Spelling counts: sagittal · cribriform · sternocleidomastoid · tensor veli palatini · carotid sheath · sphincter pupillae · superior orbital fissure · ptosis · hematoma.

★ High-yield traps

Middle meningeal artery → EPIDURAL hematoma — it runs between the skull and the dura. Lens-shaped; does not cross sutures. Subdural = bridging veins.
Dural venous sinuses form where the two dural layers (periosteal + meningeal) fail to fuse at the edges of dural folds.
Falx = left/right. Tentorium = up/down. Falx cerebri anchors to the crista galli of the ethmoid.
CN VI runs through the cavernous sinus (next to the internal carotid artery) → first affected. CN III, IV, V1, V2 are in the lateral wall. CN V3 is not in the sinus.
Palatoglossus = CN X (the only tongue muscle not supplied by CN XII). Styloglossus = CN XII. Stylopharyngeus = CN IX.
Light reflex: afferent CN II, efferent CN III. Corneal reflex: afferent CN V1, efferent CN VII. Gag: afferent CN IX, efferent CN X.
CN VIII never leaves the skull — it ends in the inner ear within the petrous temporal bone.
Tongue deviates toward a CN XII lesion; uvula deviates away from a CN X lesion; jaw deviates toward a CN V3 lesion.

2 · Meninges, Dural Folds & Dural Venous Sinuses

Coronal schematic, not to scale. Superficial → deep: skull · dura (periosteal + meningeal) · arachnoid · pia · brain.

Dura mater

Tough, “tarp-like”; attaches to the inside of the skull and holds the brain in place. Two layers: periosteal (outer) + meningeal (inner). Dura = durable.

Arachnoid mater

Delicate, thin, spider-web-like middle layer. Arachnoid = arachnid.

Pia mater

Soft, highly vascular; adheres to the brain and follows every contour — can’t be dissected away. Pia = pious, clings to the brain.

Outside → in: “DAP” — Dura, Arachnoid, Pia.

Dural folds

Fold	Orientation	Separates	Hook
Falx cerebri	Vertical, midline, sickle-shaped	Left ↔ right cerebral hemispheres	Anchors to the crista galli of the ethmoid bone
Tentorium cerebelli	Horizontal “tent”	Cerebrum (above) ↔ cerebellum (below)	Tent roofing the cerebellum
Falx cerebelli	Vertical, midline, small	Left ↔ right cerebellar hemispheres	Small sickle for the small brain

“Falx = left/right. Tentorium = up/down.” Then ask: cerebrum or cerebellum?

Dural venous sinuses

What to know

Formation: at the edges of dural folds the periosteal and meningeal layers don’t fuse → open channels for venous blood. Split the sheet → sinus.
They leave grooves on the inner skull (osteology list: grooves for the superior sagittal, transverse and sigmoid sinuses).
No valves → blood can flow in either direction → infection can travel back into the cranium (danger triangle, scalp emissary veins).
Sit between the dural layers (not in the subarachnoid space) and drain toward the internal jugular vein.

Sinus	Where to find it
Superior sagittal	Upper attached edge of the falx cerebri; groove on the inner skull (incl. occipital bone)
Inferior sagittal	Lower free edge of the falx cerebri
Straight	Where the falx cerebri meets the tentorium cerebelli
Confluence of sinuses	Occipital bone (internal occipital protuberance) — meeting point at the back of the head
Transverse (R + L)	Run laterally from the confluence; groove on the occipital bone
Sigmoid	S-shaped continuation → jugular foramen → internal jugular vein
Cavernous	Either side of the sella turcica (see Section 3)

Orientation map (positions as labeled in lecture):

Superior sagittal sinus→Confluence of sinuses→Transverse sinuses→Sigmoid sinus→Internal jugular vein (jugular foramen)

“Super Cool Trains Stop at Junctions.”

3 · Cavernous Sinus

CN V3 does not pass through the cavernous sinus — it leaves via the foramen ovale.

Through the sinus: internal carotid artery + sympathetic carotid plexus + CN VI

In the lateral wall (top → bottom): CN III → IV → V1 → V2

Receives: cerebral veins · ophthalmic veins · pterygoid plexus (emissary veins via foramen ovale / lacerum)

Cavernous sinus syndrome

Ophthalmoplegia — CN III, IV, VI
Ptosis — CN III + sympathetics
Absent pupillary response — CN III
Loss of corneal + maxillary sensation — CN V1, V2
Horner syndrome — sympathetic plexus
CN VI usually first (free in the sinus)

Routes of infection → thrombophlebitis

Facial vein→Ophthalmic veins→Cavernous sinus

Deep facial vein→Pterygoid plexus→Emissary veins→Cavernous sinus

Ethmoid / sphenoid sinusitis→Orbital veins→Cavernous sinus

Signs: lid swelling, proptosis, extraocular muscle impairment.

Pituitary tumor

Lateral extension into the cavernous sinus compresses CN VI, V1 and V2.

Surgical access: trans-nasal, trans-sphenoidal route through the sphenoid sinus.

4 · Arteries

Internal carotid artery

Common carotid artery→Internal carotid arteryno branches in the neck→Carotid canal→Through cavernous sinus (with CN VI)→Ophthalmic artery→Optic canal (with CN II)

Carries the sympathetic carotid plexus (from the superior cervical ganglion) → damage = Horner syndrome: Ptosis (mild), Anhidrosis (no sweating), Miosis (small pupil) — same side.

Vertebral artery

Subclavian artery (1st part)→medial to anterior scaleneTransverse foramina C6 → C1→Foramen magnum→Joins partner → basilar artery

Subclavian artery branches — “VITamin C, D”
Part 1 (medial to anterior scalene)	Vertebral · Internal thoracic · Thyrocervical trunk	Thyrocervical → inferior thyroid, suprascapular, transverse cervical
Part 2 (behind)	Costocervical trunk
Part 3 (lateral)	Dorsal scapular	Often from transverse cervical instead

Middle meningeal artery

Maxillary artery (part 1)→encircled by auriculotemporal nerveForamen spinosum→Between skull & dura, deep to pterion→Supplies dura + calvaria

	Epidural hematoma	Subdural hematoma
Vessel	Middle meningeal artery (pterion fracture)	Bridging veins
Space	Skull ↔ dura	Under the dura
CT	Biconvex / lens	Crescent
Sutures	Does not cross — dura is “stapled” to the skull at sutures	Crosses

Epi- = “on top of” the dura → where the middle meningeal artery lives.

Opening	Artery
Carotid canal	Internal carotid artery (+ sympathetic plexus)
Foramen magnum	Vertebral arteries
Foramen spinosum	Middle meningeal artery
Optic canal	Ophthalmic artery (+ CN II)

5 · Cranial Nerves at a Glance

CN	Fossa	Opening	Modality	Key function / high-yield
I Olfactory	Anterior	Cribriform foramina (cribriform plate, ethmoid)	Special sensory	Smell; olfactory epithelium in roof of nasal cavity; fracture → anosmia
II Optic	Middle	Optic canal (lesser wing, sphenoid)	Special sensory	Vision; with ophthalmic artery; afferent of light reflex
III Oculomotor	Middle	Superior orbital fissure	Motor + parasympathetic	LPS, SR, IR, MR, IO + ciliary ganglion → sphincter pupillae, ciliary muscle
IV Trochlear	Middle	Superior orbital fissure	Motor	Superior oblique
V1 Ophthalmic	Middle	Superior orbital fissure	General sensory	Frontal, lacrimal, nasociliary (“NFL”); forehead, upper lid, cornea, tip of nose
V2 Maxillary	Middle	Foramen rotundum → pterygopalatine fossa	General sensory	Midface, upper lip, upper teeth, palate, maxillary sinus
V3 Mandibular	Middle	Foramen ovale → infratemporal fossa	General sensory + branchial motor	8 muscles; lower face, anterior 2/3 tongue (general sensation)
VI Abducens	Middle	Superior orbital fissure	Motor	Lateral rectus
VII Facial	Posterior	Internal acoustic meatus → stylomastoid foramen	All four	Face, taste ant. 2/3, tears, saliva, stapedius
VIII Vestibulocochlear	Posterior	Internal acoustic meatus (stays in temporal bone)	Special sensory	Hearing + balance
IX Glossopharyngeal	Posterior	Jugular foramen	All four	Stylopharyngeus, parotid, post. 1/3 tongue, carotid sinus/body
X Vagus	Posterior	Jugular foramen	All four	Palate, pharynx, larynx, palatoglossus; thorax/abdomen
XI Accessory	Posterior	Jugular foramen (spinal root enters via foramen magnum)	Motor	Sternocleidomastoid, trapezius
XII Hypoglossal	Posterior	Hypoglossal canal (occipital)	Motor	Tongue muscles except palatoglossus

Superior orbital fissure

CN III, IV, V1, VI
“Standing Room Only” — V1 SOF, V2 Rotundum, V3 Ovale

Internal acoustic meatus

CN VII + CN VIII
Tumor here → CN VII deficits + hearing loss, tinnitus, vertigo

Jugular foramen

CN IX, X, XI + internal jugular vein (from sigmoid sinus)

Trigeminal ganglion (sensory ganglion of CN V) sits in the middle cranial fossa; V1, V2 and V3 leave it.

6 · Eye Nerves & Palsies

	CN III palsy	CN IV palsy	CN VI palsy
Muscle(s) lost	LPS, SR, IR, MR, IO + sphincter pupillae, ciliary	Superior oblique	Lateral rectus
Eye position	Down and out (SO + LR unopposed)	Affected eye slightly up	Turned in (MR unopposed)
Eyelid / pupil	Complete ptosis, dilated pupil	Normal	Normal
Diplopia	Multiple directions	Vertical, worse looking down and in (reading, stairs); head tilts away	Horizontal, worse looking toward the lesion
Test	—	Look in, then down	Look out

	Constrict (miosis)	Dilate (mydriasis)
Muscle	Sphincter pupillae (circular)	Dilator pupillae (radial)
System	Parasympathetic — CN III → ciliary ganglion → short ciliary nerves	Sympathetic — superior cervical ganglion → carotid plexus → long ciliary nerves
Lesion	CN III palsy → dilated pupil + complete ptosis	Horner → small pupil + mild ptosis + anhidrosis

Sphincter = Squeeze = Small pupil. Parasympathetic side pairs with LPS; sympathetic side pairs with the superior tarsal (Müller’s) muscle.

7 · Reflexes

Light:Light→CN II→Brainstem (both sides)→CN III→Ciliary ganglion→Sphincter pupillae (both pupils)

Near:Near object→CN II→CN III→Converge (MR) · Accommodate (ciliary) · Constrict (sphincter)

Corneal:Touch cornea→Long ciliary → nasociliary → CN V1→CN VII (temporal + zygomatic)→Orbicularis oculi · both eyes blink

Gag:Touch oropharynx→CN IX→CN X→Pharyngeal constrictors

Reflex	Afferent	Efferent	Ganglion	Afferent lesion test
Light	CN II	CN III	Ciliary	Light in bad eye → neither pupil constricts; light in good eye → both constrict
Near	CN II	CN III	Ciliary	“Converge, Accommodate, Constrict”
Corneal	CN V1	CN VII	None (somatic motor)	Touch affected cornea → no blink in either eye
Gag	CN IX	CN X	—	Touch affected side → no gag; normal side → normal gag

“2 in, 3 out” (pupil) · “5 in, 7 out” (blink) · “9 in, 10 out” (gag).

8 · CN IX · X · XI · XII

CN IX — glossopharyngeal

1 muscle: stylopharyngeus — elevates pharynx + larynx
1 gland: parotid
Tongue: taste + general sensation, posterior 1/3; oropharynx sensation
Carotid sinus (blood pressure) + carotid body (O₂/CO₂/pH)
Afferent limb of gag

CN IX→Lesser petrosal→Otic ganglion→Auriculotemporal (V3)→Parotid

CN X — vagus

In the carotid sheath, posterior, between the carotid artery and internal jugular vein
Palate muscles except tensor veli palatini (CN V3)
Pharynx muscles except stylopharyngeus (CN IX)
Larynx muscles; palatoglossus
Lesion: uvula deviates away; recurrent laryngeal → hoarseness
Efferent limb of gag; taste from the epiglottis region

CN XI — accessory

Spinal root up through foramen magnum, out through jugular foramen
Sternocleidomastoid (turn head to opposite side) + trapezius (shrug)
Most exposed in the posterior triangle (lymph node biopsy) → usually trapezius only: shoulder droop, weak shrug

CN XII — hypoglossal

Hypoglossal canal (occipital bone)
All intrinsic + extrinsic tongue muscles except palatoglossus
Lesion: tongue deviates toward the lesion (opposite genioglossus unopposed)
Lateral to hyoglossus; lingual artery deep (medial) to it
Carries C1 fibers → thyrohyoid, geniohyoid, superior root of ansa cervicalis

Muscle	Nerve	Hook
Styloglossus · hyoglossus · genioglossus · intrinsic tongue	CN XII	All -glossus = XII…
Palatoglossus	CN X	…except PALatoglossus, CN X’s PAL
Stylopharyngeus	CN IX	CN IX’s only muscle
Stylohyoid	CN VII	Stylo- muscles: glossus XII, pharyngeus IX, hyoid VII
Tensor veli palatini	CN V3	Tensor = Trigeminal

9 · More Comparisons

Lesion site	Nerves hit	Findings
Internal acoustic meatus	CN VII + VIII	Whole-face paralysis, dry eye, ↓ saliva, loss of taste ant. 2/3, hyperacusis, loss of blink (efferent) + hearing loss, tinnitus, vertigo
Jugular foramen	CN IX + X + XI	Loss of gag (afferent), uvula away, hoarseness, weak SCM + trapezius
Cavernous sinus	CN III, IV, V1, V2, VI + sympathetics	Ophthalmoplegia, ptosis, fixed pupil, ↓ corneal/maxillary sensation, Horner; CN VI first
Cribriform plate fracture	CN I	Anosmia

Which way does it deviate?	Direction	Why
Tongue (CN XII lesion)	Toward lesion	Healthy genioglossus pushes across
Jaw (CN V3 lesion)	Toward lesion	Healthy lateral pterygoid pushes across
Uvula (CN X lesion)	Away from lesion	Healthy side pulls it over

Tongue and jaw are “pushed” → toward. Uvula is “pulled” → away.

10 · Clinical Correlations

Scenario	Structure	Answer
Temple blow, lens-shaped bleed on CT	Middle meningeal artery (pterion)	Epidural hematoma; artery entered via foramen spinosum
Nose pimple → fever, proptosis, lateral gaze palsy	Cavernous sinus	Thrombophlebitis; CN VI first
Ethmoid sinusitis → lid swelling, proptosis, eye muscle weakness	Orbital veins → cavernous sinus	Retrograde spread through valveless veins
Pituitary mass + lateral gaze palsy + numb forehead/cheek	Cavernous sinus	Compression of CN VI, V1, V2
Ptosis, miosis, anhidrosis	Sympathetic carotid plexus	Horner syndrome
Eye down and out, complete ptosis, dilated pupil	CN III	Oculomotor palsy
Trouble reading / going downstairs, head tilt	CN IV	Superior oblique palsy
Shingles on forehead + tip of nose	Nasociliary nerve (V1)	Hutchinson sign → risk of eye involvement
Loss of smell after head trauma	CN I at cribriform plate	Anosmia
Shoulder droop after posterior triangle lymph node biopsy	CN XI	Trapezius weakness
Hoarseness, uvula deviates to the right	Left CN X	Vagus lesion (recurrent laryngeal)
Scalp infection spreading inward → black eyes	Emissary veins / loose areolar layer	Connects to dural venous sinuses

11 · Self-Check Questions

Answer first, then open each one to check.

1. List the meninges from superficial to deep, and the two layers of the dura.

Dura (periosteal + meningeal layers) → arachnoid → pia.

2. How does a dural venous sinus form?

At the edges of dural folds the periosteal and meningeal layers don’t fuse, leaving an open venous channel.

3. What does the falx cerebri separate, and where does it anchor anteriorly?

Left and right cerebral hemispheres; the crista galli of the ethmoid bone.

4. What does the tentorium cerebelli separate?

Cerebrum (above) from cerebellum (below).

5. Which nerve runs through the cavernous sinus rather than in its wall, and why does that matter?

CN VI — it lies free next to the internal carotid artery and is usually affected first.

6. A pterion fracture tears which artery, causing which hematoma, with what CT shape?

Middle meningeal artery → epidural hematoma → biconvex/lens-shaped, doesn’t cross sutures.

7. Through which opening does the internal carotid artery enter the skull, and which branch goes to the orbit?

Carotid canal; the ophthalmic artery, through the optic canal with CN II.

8. Which three nerves and which vein pass through the jugular foramen?

CN IX, X, XI and the internal jugular vein (continuation of the sigmoid sinus).

9. Which tongue muscle is not supplied by CN XII?

Palatoglossus — CN X.

10. Name the afferent and efferent limbs of the light, corneal and gag reflexes.

Light: II → III. Corneal: V1 → VII. Gag: IX → X.

11. Where is the sensory ganglion of CN V?

Trigeminal ganglion, middle cranial fossa.

12. A pituitary tumor extends laterally. Which nerves are compressed?

CN VI, V1 and V2 (in the cavernous sinus).

HoyaDocs · HNSS Lab 3 Exam-Day ReviewUpdated 27 Sep 2026 · Rev 1.0