Corpus: Lacrimal nerve

The lacrimal nerve is the smallest branch of the ophthalmic nerve (V1), a division of the trigeminal nerve.

The lacrimal nerve branches off from the ophthalmic nerve in the middle cranial fossa and runs in its own dural protrusion to the superior orbital fissure. It enters the eye socket (orbit) through the narrowest part of the fissure.

Within the orbit, the lacrimal nerve runs forward (rostrally) along the upper edge of the lateral rectus muscle, accompanied by the lacrimal artery. It communicates via a small branch (ramus communicans) with the zygomaticotemporal nerve, from which it receives postganglionic parasympathetic fibers originating from the facial nerve (cranial nerve VII) via the pterygopalatine ganglion.

Upon reaching the lacrimal gland, the lacrimal nerve releases numerous fine branches into its tissue. It then pierces the orbital septum and terminates in the skin of the upper eyelid, where it communicates with fibers from the facial nerve.

The lacrimal nerve supplies sensation to the conjunctiva, the skin of the lateral upper eyelid, and the lateral corner of the eye. It also innervates the lacrimal gland with parasympathetic fibers from the pterygopalatine ganglion and sympathetic fibers from the internal carotid plexus.