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7. Describe the dermatomes of the face & head. Which divisions of the trigeminal n. (CN V) serve these dermatomes, and what are the major terminal cutaneous nerves of the face?
7. Describe the dermatomes of the face & head. Which divisions of the trigeminal n. (CN V) serve these dermatomes, and what are the major terminal cutaneous nerves of the face?
The trigeminal n. (CN V) is responsible for innervating muscles of mastication (efferent) and sensation of the skin of the face (afferent). The trigeminal n. has three divisions: ophthalmic n. (V1), maxillary n. (V2), and mandibular n. (V3). The complete courses and functions of these divisions will be discussed elsewhere, but there are five nerves of these divisions afferently serving the skin of the face: the supra-orbital n. & supratrochlear [supratrochlear will discussed in more detail in Session 10] (V1), the infra-orbital n. (V2), the mental n. (V3), and the cutaneous portion of the auriculotemporal n. (V3).
The supra-orbital n. is the terminal continuation of the frontal n. through the supra-orbital notch or foramen, which afferently serves the conjunctiva, mucosa of the frontal sinus, and skin of the superior palpebra, forehead, and epicranial scalp. The supra-orbital n. is a branch of the ophthalmic n. (V1). Variations of crania include those with supra-orbital notches and those with supra-orbital foramen. Either of these structures, when present, are found along the superior rim of the orbit, nearly halfway between the midpoint of the superior rim and the medial rim of the orbit.
The infra-orbital n. is the branch of the maxillary n. (V2) which exits the infra-orbital foramen of the maxilla. The infra-orbital foramen is below the orbit, approximately in-line with (or just lateral) to the supra-orbital foramen (or notch) above. The infra-orbital n. afferently supplies the mucosa of the maxillary sinus and gingiva, and skin of the: inferior palpebra, the lateral nose, upper lip, and cheek.
The mental n. is the terminal continuation of the inferior alveolar n., a branch of the mandibular n. (V3), which passes through the mental foramen of the mandible to afferently serve the mandibular gingiva, and skin of the: lower lip and chin.
The auriculotemporal n. is also a branch of the mandibular n. (V3). The auriculotemporal n. serves many functions, but germane to this session, it afferently serves the skin of the: tragus of the ear, the external auditory meatus, and the area anterosuperior to the ear. The cutaneous portion of the auriculotemporal n. may be found accompanying the superficial temporal a. and v. superiorly from the parotid gland.
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