The trigeminal nerve is the fifth of twelve pairs of cranial nerves enervating the face and head, and is denoted by the Roman Numeral V. It has three divisions which enervate the forehead and eye (ophthalmic V1), cheek (maxillary V2) and lower face and jaw (mandibular V3). The trigeminal nerves function in sensing facial touch, pain and temperature, as well as controlling muscles used for chewing. The trigeminal nerve functions should be distinguished from the facial nerve (cranial nerve VII), which controls all other facial movements. The ophthalmic nerve (V1) is one of the three branches of the trigeminal nerve, the fifth cranial nerve. Like the maxillary branch of the trigeminal nerve, the ophthalmic branch carries sensory fibers only. Branches
• Nasociliary nerve
o sensory root of ciliary ganglion
o posterior ethmodial nerve
o long ciliary nerve
o infratrochlear nerve
o anterior ethmoidal nerve
• lacrimal nerve
• frontal nerve
o supratrochlear nerve
o supraorbital nerve
The nasociliary nerve is a branch of the ophthalmic nerve. It is intermediate in size between the two other main branches of the ophthalmic nerve, the frontal nerve and the lacrimal nerve, and is more deeply placed. The nasociliary nerve enters the orbit between the two heads of the lateral rectus muscles and between the superior and inferior rami of the oculomotor nerve (CN III). It passes across the optic nerve (CN II) and runs obliquely beneath the superior rectus muscle and superior oblique muscle to the medial wall of the orbital cavity. After giving the posterior ethmoidal nerve and anterior ethmoidal nerve, it terminates as the infratrochlear nerve on the medial margin of the orbit.
The nasociliary nerve gives off the following branches:
• posterior ethmoidal nerve
• long ciliary nerves
• infratrochlear nerve
• communicating branch to the ciliary ganglion (long root of the ciliary ganglion) • anterior ethmoidal nerve
Posterior ethmoidal nerve
The posterior ethmoidal nerve is a branch of the nasociliary nerve. It passes through the posterior ethmoidal foramen, with the posterior ethmoidal artery. It carries sensory information from the sphenoid sinus and posterior ethmoidal air cells. It is absent in about 30% of people.
Long ciliary nerves
The long ciliary nerves, two or three in number, are given off from the nasociliary, as it crosses the optic nerve. They accompany the short ciliary nerves from the ciliary ganglion, pierce the posterior part of the sclera, and running forward between it and the choroid, are distributed to the iris and cornea. The long ciliary nerves provide sensory innervation to the eyeball. In addition, they contain sympathetic fibers from the superior cervical ganglion to the dilator pupillæ muscle. The sympathetic fibers to the dilator pupillae muscle mainly travel in the nasociliary nerve but there are also sympathetic fibers in the short ciliary nerves that pass through the ciliary ganglion without forming synapses. Infratrochlear nerve
The infratrochlear nerve is given off from the nasociliary just before it enters the anterior ethmoidal foramen. It runs forward along the upper border of the medial rectus, and is joined, near the pulley of the superior oblique, by a filament from the supratrochlear nerve. It then passes to the medial commissure of the eye, and supplies the skin of the eyelids and side of the nose, the conjunctiva, lacrimal sac, and caruncle.
Sensory root of ciliary ganglion
Sensory fibers from the eyeball (the cornea, iris and ciliary body) run posteriorly through the short ciliary nerves and pass through the ciliary ganglion without forming synapses. They leave the ciliary ganglion in the sensory root of ciliary ganglion, which joins the nasociliary nerve. The nasociliary nerve is a branch of the ophthalmic nerve, one...