The fifth cranial nerve, also known as the trigeminal nerve, has three main divisions. The first division, V1, or the ophthalmic nerve, is responsible for sensation to the upper one-third of the face including the anterior scalp, forehead, upper eyelid, conjunctiva, cornea, frontal/ethmoid sinus, lacrimal gland, dorsum and tip of the nose. V1 is also involved in the sensory limb of the corneal reflex.
The second division, the maxillary nerve or V2, is sensory as well, and its distribution includes the midface, lower eyelid, cheek, nasopharynx, upper lip/teeth/gums, and palate. The third division, the mandibular nerve or V3, has both motor and sensory components, including sensation to the anterior two-thirds of the tongue, as well as the lower one-third of the face. This includes the lower lip, teeth/gums, and chin, along with the anterior, inferior, and superior aspects of the external auditory canal. The motor portion of V3 supplies the muscles of mastication. It also innervates the tensor tympani.
The trigeminal nerve, also known as cranial nerve V, has three major divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3). V1 and V2 are sensory while V3 has both sensory and motor components.
The ophthalmic nerve, the first division of the trigeminal nerve, primarily carries sensory information from the scalp and forehead, the upper eyelid, the conjunctiva and cornea of the eye, the nose (including the tip of the nose), the frontal sinuses and parts of the meninges.
The maxillary nerve is the second division of cranial nerve V, the trigeminal nerve. It carries sensory information from the midface, lower eyelid, cheek, nasopharynx, upper lip/teeth/gums, and palate. This nerve plays a crucial role in transmitting sensory information towards the brain.
The corneal reflex is a protective response to the cornea (the transparent layer forming the front of the eye) upon contact. In this reflex, sensory information is conveyed from the cornea back to the brain via the ophthalmic (V1) division of the trigeminal nerve. A motor response is generated through the facial nerve (cranial nerve VII) to blink the eyelids.