The upper lip is supplied by branch from maxillary neve white lower lip is supplied by which of the following nerves?
a. Buccal branch of facial nerve
b. Buccal branch of mandibular nerve .
c. Mandibular branch of Facial nerve
d. Inferior alveolar nerve
e. Mental nerve
The correct answer and explanation is:
The correct answer is e. Mental nerve.
The mental nerve is a branch of the inferior alveolar nerve, which is a branch of the mandibular division of the trigeminal nerve (cranial nerve V). The mental nerve supplies sensory innervation to the skin of the lower lip, chin, and the mucous membrane of the lower lip. It provides sensation to these areas, including touch, pain, and temperature.
The trigeminal nerve is responsible for sensation in the face, and its three branches—ophthalmic (V1), maxillary (V2), and mandibular (V3)—cover different regions. The mandibular nerve (V3) provides both motor and sensory innervation. The sensory component of the mandibular nerve includes several important branches, including the inferior alveolar nerve, which supplies the lower teeth and gums and eventually branches into the mental nerve.
The mental nerve exits the mandible via the mental foramen, located near the premolar teeth, and supplies the lower lip and chin with sensation. It also contributes to the sensory input from the mucosal lining of the lower lip. This nerve is purely sensory and does not have any motor function.
The other options listed in the question are incorrect because:
- a. Buccal branch of the facial nerve: The buccal branch of the facial nerve is a motor nerve that innervates the muscles of facial expression, not the lower lip.
- b. Buccal branch of the mandibular nerve: This branch provides sensation to the mucous membrane of the cheek and not the lower lip.
- c. Mandibular branch of the facial nerve: This nerve does not exist, as the facial nerve (cranial nerve VII) does not have a mandibular branch.
- d. Inferior alveolar nerve: While it is responsible for sensory innervation of the lower teeth, it does not supply the lower lip directly. It becomes the mental nerve after passing through the mandibular foramen and supplying the lower lip.
Thus, the mental nerve is the main sensory nerve for the lower lip.