Anatomy clinical correlates: Trigeminal nerve (CN V)

The trigeminal nerve is the fifth cranial nerve. It provides both sensory and motor functions, while also serving as a highway for parasympathetic innervation.

This is the nerve that allows you to feel wonderful things, like the kiss of your partner,

or a summer breeze on your face,

but also less pleasant things, like a dentist drilling into your teeth.

Luckily, understanding the anatomy and distribution of the trigeminal nerve can help us better diagnose and manage several conditions - and it even makes going to the dentist less painful!

First off, let’s remember some important anatomical features of the trigeminal nerve. The trigeminal nerve has three divisions: the ophthalmic or V1, the maxillary or V2, and the mandibular division or V3.

Through its branches, the trigeminal nerve supplies sensory innervation to the skin of the entire face, the mucosa of sinuses, as well as the nasal, and oral cavities. It also carries the sensory fibers for taste which go on to travel with the chorda tympani branch of cranial nerve VII, or the facial nerve.

The trigeminal nerve also carries parasympathetic innervation to the ciliary body and sphincter pupillae, the lacrimal gland, the nasal glands, palatal salivary glands, and the parotid, submandibular, and sublingual glands., though these parasympathetic fibres originally arise from other cranial nerves.

Finally, the trigeminal nerve supplies motor innervation to the muscles of mastication. And if all that wasn’t enough, the trigeminal nerve is also involved in the corneal reflex, also known as the blink reflex, which causes involuntary blinking when the cornea is stimulated to protect the eye from foreign bodies, like a pesky grain of sand getting in your eye.