Motor and Sensory Facial Nerves
The motor nerves for the muscles of facial expression come from the facial nerve (CN VII). The muscles of mastication (the ones that move your mouth and jaw when you eat) are innervated by the mandibular nerve (motor fibers of CN V). Sensory nerves originate from a number of places, for example, sensory nerves to the skin covering the neck and posterior scalp come from the cervical nerves.
The branches of the facial nerve include the following:
Buccal branch: Innervates the muscles in the cheek and above the mouth
Cervical branch: Innervates the platysma
Marginal mandibular branch: Innervates the muscles of the lower lip and chin
Posterior auricular branch: Has branches that innervate the muscles around the ear and the occipitofrontal muscle
Temporal branch: Innervates the muscles that wrinkle the forehead, close the eyelids, and wiggle the ear
Zygomatic branches of the facial nerve: Innervate muscles that close the eye and raise the corners of the mouth
The following sensory, cutaneous nerves originate from the ophthalmic nerve (CN V1):
Supraorbital nerve: This nerve branches from the frontal nerve (largest branch of the ophthalmic nerve) and runs along the roof of the orbit, emerging from the supraorbital notch to the forehead. It innervates the frontal sinus, upper eyelid, and anterolateral part of the forehead and scalp.
Supratrochlear nerve: Branching from the frontal nerve, this nerve runs anteriorly and medially along the roof of the orbit to the forehead. It innervates the medial superior eyelid and anteromedial forehead.
Lacrimal nerve: This nerve branches from the ophthalmic nerve and runs through the orbit. It innervates the lacrimal gland and lateral part of the superior eyelid.
Infratrochlear nerve: Branching off the nasocillary nerve and running along the medial wall of the orbit, this nerve innervates the skin just lateral to the nose, the medial-most parts of the eyelids, the lacrimal sac, and the lacrimal caruncle (the red, fleshy part in the medial corner of the eye).
External nasal nerve: This nerve branches from the anterior ethmoidal nerve and runs between the nasal bone and lateral nasal cartilage. It innervates the skin of the nose.
The following three sensory, cutaneous nerves come from the maxillary nerve (CN V2):
Infraorbital nerve: This nerve comes from the maxillary nerve and runs through the orbital floor, emerging from the infraorbital foramen. It innervates the maxillary sinus, maxillary teeth, inferior eyelid, skin of the cheek, lateral nose, nasal septum, and upper lip.
Zygomaticofacial nerve: Branching from the zygomatic nerve and running along the zygomatic bone at the inferiolateral part of the orbit, this nerve exits the zygomaticofacial foramen of the zygomatic bone and innervates skin on the cheek.
Zygomaticotemporal nerve: This nerve branches off the zygomatic nerve. It exits via the zygomaticotemporal foramen of the zygomatic bone and innervates the skin over the temple.
Three more cutaneous nerves stem from the mandibular nerve (CN V3):
Auriculotemporal nerve: Branching off the mandibular nerve near the middle meningeal artery, this nerve runs posteriorly deep to the mandibular ramus and parotid gland. It innervates the skin in the posterior part of the temporal region, the skin of the auricle of the ear, the external acoustic meateus, and the external surface of the tympanic membrane.
Buccal nerve: This nerve is different from the buccal branch of the facial nerve. It branches from the mandibular nerve, runs between the pterygoid muscle, and emerges near the mandibular ramus. It innervates the skin and mucosa of the cheek and part of the gums.
Mental nerve: This nerve branches from the inferior alveolar nerve and emerges from the mandible through the mental foramen. It innervates the skin of the chin and the inside of the lower lip.
The following four sensory, cutaneous nerves are branches of the upper cervical spinal nerves:
Great auricular nerve: This nerve branches from the anterior rami of the 2nd and 3rd cervical spinal nerves and runs upward across the sternocleidomastoid posterior to the external jugular vein. It innervates the skin over the angle of the mandible, the parotid gland, and the earlobe.
Lesser occipital nerve: Also branching from the anterior rami of the 2nd and 3rd cervical spinal nerves, this nerve runs along the posterior border of the sternocleidomastoid and goes up to the ear. It innervates the scalp behind the ear.
Greater occipital nerve: Branching off the posterior ramus of the 2nd cervical spinal nerve and passing through the trapezius, this nerve innervates the scalp of the occipital area.
3rd occipital nerve: This nerve branches off the posterior ramus of the 3rd cervical nerve and pierces the trapezius. It innervates the scalp in the occipital and suboccipital areas.