The Nasociliary Nerve (n. nasociliaris; nasal nerve) is intermediate in size between the frontal and lacrimal, and is more deeply placed. It enters the orbit between the two heads of the Rectus lateralis, and between the superior and inferior rami of the oculomotor nerve. It passes across the optic nerve and runs obliquely beneath the Rectus superior and Obliquus superior, to the medial wall of the orbital cavity. Here it passes through the anterior ethmoidal foramen, and, entering the cavity of the cranium, traverses a shallow groove on the lateral margin of the front part of the cribriform plate of the ethmoid bone, and runs down, through a slit at the side of the crista galli, into the nasal cavity. It supplies internal nasal branches to the mucous membrane of the front part of the septum and lateral wall of the nasal cavity. Finally, it emerges, as the external nasal branch, between the lower border of the nasal bone and the lateral nasal cartilage, and, passing down beneath the Nasalis muscle, supplies the skin of the ala and apex of the nose.
The nasociliary nerve gives off the following branches, viz.: the long root of the ciliary ganglion, the long ciliary, and the ethmoidal nerves.