Lab 4 Exam-Day Review

✍️ Wording

Write full names (“levator palpebrae superioris,” not “LPS”; “superior orbital fissure,” not “SOF”). Cranial nerves may be written as CN III or oculomotor nerve.
Spelling counts: trochlea · levator palpebrae superioris · sphincter pupillae · nasociliary · supratrochlear · infratrochlear · periorbita · puncta · canaliculi.

★ High-yield traps

“LR6, SO4, AO3” — lateral rectus = CN VI, superior oblique = CN IV, all others (including LPS) = CN III.
Lacrimal gland: CN VII → greater petrosal nerve → pterygopalatine ganglion → zygomatic nerve (V2) → lacrimal nerve (V1) → gland. The lesser petrosal nerve is CN IX → otic ganglion → parotid.
Every orbital artery is a branch of the ophthalmic artery (from the internal carotid artery), and each travels with the nerve of the same name.
Only parasympathetic fibers synapse in the ciliary ganglion. Short ciliary nerves come from the ganglion; long ciliary nerves come from the nasociliary nerve and bypass it.
Light reflex: afferent CN II, efferent CN III. Corneal reflex: afferent CN V1 (nasociliary), efferent CN VII (bilateral).
H-test: ABduct → test the Recti · ADduct → test the Obliques.
Infratrochlear (V1, nasociliary) ≠ infraorbital (V2, orbital floor).
The orbital apex is posteromedial — the optic canal is in the lesser wing of the sphenoid.

2 · Bony Orbit, Walls & Openings

Seven bones form the orbit: frontal, zygomatic, maxilla, lacrimal, ethmoid, sphenoid, palatine. It’s a four-sided pyramid: broad base at the orbital margin, apex at the optic canal (posteromedial). The eyeball fills only the anterior half; the posterior half is orbital fat, extraocular muscles, nerves and vessels. The periorbita is the periosteum lining the orbit.

Opening	Location	Contents
Optic canal	Lesser wing of sphenoid (apex)	CN II + ophthalmic artery
Superior orbital fissure	Between lesser & greater wings of sphenoid	CN III, IV, VI · frontal, lacrimal, nasociliary nerves (V1) · superior ophthalmic vein
Inferior orbital fissure	Between sphenoid & maxilla	Zygomatic + infraorbital nerves (V2) · infraorbital artery · inferior ophthalmic vein
Supraorbital notch/foramen	Superior orbital margin, frontal bone	Supraorbital nerve (V1) + artery
Infraorbital foramen	Maxilla, below the orbit	Infraorbital nerve (V2) + artery
Anterior ethmoidal foramen	Medial wall	Anterior ethmoidal nerve (V1) + artery
Posterior ethmoidal foramen	Medial wall	Posterior ethmoidal nerve (V1) + artery

Fissure = slit · foramen = hole · canal = tube. Superior vein → superior fissure; inferior vein → inferior fissure.

3 · Lacrimal Apparatus

Tear flow

Drain analogy

Puncta = drain holes · canaliculi = small pipes · lacrimal sac = collecting trap · nasolacrimal duct = main pipe → inferior meatus (why your nose runs when you cry).

Nearby surface structures

The lacrimal caruncle sits at the medial corner but is not part of the drainage pathway.

Secretomotor (parasympathetic) supply

4 · Extraocular Muscles

Seven voluntary muscles: 4 recti, 2 obliques, and levator palpebrae superioris. All but the inferior oblique arise near the orbital apex; the inferior oblique arises from the anterior orbital floor.

Muscle	Primary	Secondary	Nerve	H-test
Medial rectus	Adduction	—	CN III	—
Lateral rectus	Abduction	—	CN VI	—
Superior rectus	Elevation	Adduction, intorsion	CN III	Abduct → look up
Inferior rectus	Depression	Adduction, extorsion	CN III	Abduct → look down
Superior oblique (tendon through the trochlea)	Depression	Abduction, intorsion	CN IV	Adduct → look down
Inferior oblique	Elevation	Abduction, extorsion	CN III	Adduct → look up
Levator palpebrae superioris	Elevates the upper eyelid (lies above superior rectus — a lab landmark)		CN III	—

Pairing rules

SR + IR both adduct
SO + IO both abduct
SR + SO both intort — “Superiors INtort”
IR + IO both extort

Why secondary actions?

The orbital axis angles posteromedially while the optical axis points straight ahead, so SR, IR and the obliques pull at an angle. Moving the eye into abduction or adduction lines a muscle up with its pull — that’s the H-test.

5 · Palsies & the Eyelid

	CN III	CN IV	CN VI
Lost	SR, IR, MR, IO, LPS + sphincter pupillae + ciliary	Superior oblique	Lateral rectus
Eye position	Down and out (SO + LR unopposed)	Slightly up	Turned in
Lid / pupil	Complete ptosis, dilated pupil, no accommodation	Normal	Normal
Diplopia	Multiple directions	Vertical, worst looking down and in (reading, stairs); head tilts away	Horizontal, worst looking out toward the lesion
Lab landmark	Branches to SR/LPS above and MR/IR/IO below	Tiny nerve ending in superior oblique	On the inner surface of lateral rectus

Eyelid openers vs closer

LPS (skeletal)←CN III

Superior tarsal muscle (smooth)←Sympathetics

Orbicularis oculi (closes)←CN VII

Layers front → back: skin → thin subcutaneous tissue → orbicularis oculi → orbital septum/tarsus → conjunctiva.

Ptosis: CN III vs Horner

	CN III	Horner
Ptosis	Complete (LPS)	Mild (superior tarsal)
Pupil	Dilated	Small (miosis)
Other	Down and out	Anhidrosis

6 · CN V1 in the Orbit — “NFL”

CN V1 (ophthalmic division) — enters through the superior orbital fissure

N · Nasociliary nerve

Crosses over CN II toward the medial wall

Anterior ethmoidal nerve → anterior ethmoidal foramen → ends as external nasal nerve (tip of nose)
Posterior ethmoidal nerve → posterior ethmoidal foramen
Infratrochlear nerve → medial corner of the eye (below trochlea)
Long ciliary nerves → eyeball (cornea), bypass the ganglion
Sensory root to the ciliary ganglion

F · Frontal nerve

Largest; on top of LPS along the roof

Supraorbital nerve (lateral) → supraorbital notch/foramen (frontal bone) → forehead, scalp, upper lid
Supratrochlear nerve (medial) → above the trochlea → medial forehead

L · Lacrimal nerve

Along the upper lateral wall

Sensory: lateral upper lid, conjunctiva, gland region
Receives the communicating branch from the zygomatic nerve (V2) → carries postganglionic secretomotor fibers to the lacrimal gland
Lab landmark: find the lacrimal gland first

CN V2 in the orbit: the zygomatic nerve (→ zygomaticofacial + zygomaticotemporal) and infraorbital nerve enter through the inferior orbital fissure; the infraorbital nerve runs in the floor and exits the infraorbital foramen.

7 · Ciliary Ganglion & Ciliary Nerves

A tiny parasympathetic ganglion in the posterior orbit, lateral to the optic nerve. One of the four head ganglia — “COPS”: Ciliary, Otic, Pterygopalatine, Submandibular.

	Long ciliary nerves	Short ciliary nerves
Come from	Nasociliary nerve (V1)	Ciliary ganglion
Relation to ganglion	Bypass it	Leave it
Carry	Sensory (cornea)	Postganglionic parasympathetic + sympathetic + sensory
Reflex role	Afferent limb of the corneal reflex	Efferent limb (parasympathetic) of the light reflex

Reflex	Afferent	Efferent	Effector
Pupillary light	CN II	CN III → ciliary ganglion → short ciliary nerves	Sphincter pupillae — both pupils (direct + consensual)
Accommodation	CN II	CN III	Ciliary muscle (+ sphincter, medial rectus)
Corneal blink	CN V1 (nasociliary; long ciliary nerves)	CN VII, bilateral	Orbicularis oculi

8 · Orbital Vessels

Branch of ophthalmic artery	Travels with	Exit / target
Supraorbital artery	Supraorbital nerve	Supraorbital notch/foramen → forehead
Lacrimal artery	Lacrimal nerve	Upper lateral orbit → lacrimal gland
Anterior ethmoidal artery	Anterior ethmoidal nerve	Anterior ethmoidal foramen
Posterior ethmoidal artery	Posterior ethmoidal nerve	Posterior ethmoidal foramen

Veins

Superior ophthalmic vein → superior orbital fissure.
Inferior ophthalmic vein → inferior orbital fissure.
Both connect to the cavernous sinus — valveless, so infection can spread backward.

Not in the orbit

The facial artery is an external carotid branch on the face — it does not supply the orbit’s contents. Orbit = ophthalmic artery (internal carotid system).

9 · Commonly Confused

Pair	Difference
Supratrochlear vs infratrochlear	Above the trochlea = frontal nerve branch · below the trochlea = nasociliary branch (both V1)
Supraorbital vs infraorbital	Supraorbital = V1 (frontal nerve), frontal bone notch · infraorbital = V2, orbital floor → maxilla
Long vs short ciliary	Long = nasociliary, bypass ganglion · short = from the ganglion
Greater vs lesser petrosal	Greater = CN VII → pterygopalatine → lacrimal gland · lesser = CN IX → otic → parotid
Superior vs inferior ophthalmic vein	Superior orbital fissure vs inferior orbital fissure
Inferior rectus paralyzed vs trapped	Paralyzed → can’t look down · trapped in floor fracture → tethered, can’t look up
Floor vs medial wall blowout	Floor → maxillary sinus (+ infraorbital nerve) · medial → ethmoidal air cells
Tarsal glands vs ciliary glands	Tarsal (in tarsus) → chalazion, deep and painless · ciliary (eyelash follicles) → stye, painful at the margin

10 · Clinical Correlations

Scenario	Structure	Answer
Blunt trauma → diplopia, sunken/low eye, numb cheek	Orbital floor + infraorbital nerve	Blowout fracture into the maxillary sinus; hypoglobus / enophthalmos
Can’t look up after orbital floor fracture	Inferior rectus	Entrapment (tethered)
Ethmoid sinusitis → lid swelling, proptosis, weak eye movements	Orbital veins → cavernous sinus	Thrombophlebitis
Eye down and out, complete ptosis, dilated pupil	CN III	Oculomotor palsy
Trouble reading / going downstairs; head tilted away	CN IV	Superior oblique palsy
Eye turned in; double vision looking toward the lesion	CN VI	Lateral rectus palsy
Mild ptosis, small pupil, dry face on one side	Sympathetic pathway	Horner syndrome
Light in right eye → no constriction of either pupil; light in left → both constrict	Right CN II	Afferent pupillary defect
Shingles on the forehead + tip of the nose	Nasociliary nerve	Hutchinson sign → ocular risk
Dry eye after a lesion of the greater petrosal nerve	Lacrimal secretomotor pathway	No tears
Deep, painless eyelid lump	Tarsal gland	Chalazion
Painful red bump at the lash line	Ciliary gland	Stye (hordeolum)