What is the optic nerve and what are its key anatomical relations in the orbit?

The optic nerve (CN II) is a sensory nerve that transmits visual information from the eyeball to the brain. In the orbit, it is crossed superiorly by the superior ophthalmic vein, ophthalmic artery, and nasociliary nerve (remembered by the mnemonic VAN).

How does the oculomotor nerve enter the orbit and what structures does it innervate?

The oculomotor nerve (CN III) enters the orbit through the superior orbital fissure within the common tendinous ring. It divides into a superior division (innervating superior rectus and levator palpebrae superioris) and an inferior division (innervating medial rectus, inferior rectus, and inferior oblique, plus parasympathetic fibers to the ciliary ganglion).

What is the function of the trochlear nerve in the orbit?

The trochlear nerve (CN IV) is a motor nerve that enters the orbit above the common tendinous ring via the superior orbital fissure. It innervates the superior oblique muscle to assist in eye movement.

Which muscle does the abducent nerve supply in the orbit?

The abducent nerve (CN VI) enters the orbit through the superior orbital fissure within the common tendinous ring. It supplies the lateral rectus muscle, which abducts the eye (moves it laterally).

What are the main branches of the ophthalmic nerve and their functions?

The ophthalmic nerve (V1) is the sensory division of the trigeminal nerve. Its main branches are the lacrimal nerve (supplying lacrimal gland and eyelid), frontal nerve (with supraorbital and supratrochlear branches for scalp and forehead), and nasociliary nerve (sensory to various orbital and nasal structures).

What is the ciliary ganglion and what are its functional components?

The ciliary ganglion is a parasympathetic ganglion near the orbital apex. It has motor (parasympathetic for pupil constriction), sensory (from nasociliary nerve), and sympathetic (for pupil dilation) roots.

Which nerves enter the orbit through the superior orbital fissure?

Nerves entering the orbit through the superior orbital fissure include the oculomotor nerve (CN III), trochlear nerve (CN IV), abducent nerve (CN VI), and branches of the ophthalmic nerve (V1).

Orbital Nerves – CN II, III, IV, VI & Ciliary Ganglion

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