Lacrimal n

Smallest of the 3 branches of the ophthalmic n. (CN V1), the lacrimal n. runs along the superior border of the lateral rectus m.  The lacrimal n. proper provides sensory innervation from the lacrimal gland and the conjunctiva, but as the nerve nears the lacrimal gland it is joined by both sympathetic and parasympathetic neurons that provide secretomotor fibers to the gland.  The parasympathetic fibers are post-ganglionic neurons from the pterygopalatine ganglion (neurons of the facial n.).  The sympathetic fibers are post-ganglionics from the superior cervical ganglion that traveled in the zygomaticofacial n (on the fact), and then passed through the small zygomaticofacial foramen on the lateral aspect of the face to reach the orbit.  Both parasympathetic and sympathetic stimulation cause lacrimation.