The maxillary nerve [V2] receives sensory branches from the dura in the middle cranial fossa, the nasopharynx, the palate, the nasal cavity, teeth of the upper jaw, maxillary sinus, and skin covering the side of the nose, the lower eyelid, the cheek, and the upper lip.
The mandibular nerve [V3] leaves the inferior margin of the trigeminal ganglion and leaves the skull through the foramen ovale (Fig. 8.53), and enters the infratemporal fossa.
The motor root of the trigeminal nerve also passes through the foramen ovale and unites with the sensory component of the mandibular nerve [V3] outside the skull. Thus the mandibular nerve [V3] is the only division of the trigeminal nerve that contains a motor component.
Outside the skull the motor fibers innervate the four muscles of mastication (temporalis, masseter, and medial and lateral pterygoids), as well as the tensor tympani muscle, the tensor veli palatini muscle, the anterior belly of the digastric muscle, and the mylohyoid muscle.
The mandibular nerve [V3] also receives sensory branches from the skin of the lower face, cheek, lower lip, anterior part of the external ear, part of the external acoustic meatus and the temporal region, the anterior two-thirds of the tongue, the teeth of the lower jaw, the mastoid air cells, the mucous membranes of the cheek, the mandible, and dura in the middle cranial fossa.
The abducent nerve [VI] carries GSE fibers to innervate the lateral rectus muscle in the orbit. It arises from the brainstem between the pons and medulla and passes forward, piercing the dura covering the clivus (Figs. 8.53 and 8.54). Continuing upward in a dural canal, it crosses the superior edge of the petrous part of the temporal bone, enters and crosses the cavernous sinus (see Fig. 8.45) just inferolateral to the internal carotid artery, and enters the orbit through the superior orbital fissure.
The facial nerve [VII] carries GSA, SA, GVE, and BE fibers:
The GSA fibers provide sensory input from part of the external acoustic meatus and deeper parts of the auricle.
The SA fibers are for taste from the anterior two-thirds of the tongue.
The GVE fibers are part of the parasympathetic part of the autonomic division of the PNS and stimulate secretomotor activity in the lacrimal gland, submandibular and sublingual salivary glands, and glands in the mucous membranes of the nasal cavity, and hard and soft palates.
The BE fibers innervate the muscles of the face (muscles of facial expression) and scalp derived from the second pharyngeal arch, and the stapedius muscle, the posterior belly of the digastric muscle, and the stylohyoid muscle.
The facial nerve [VII] attaches to the lateral surface of the brainstem, between the pons and medulla oblongata (Fig. 8.54). It consists of a large motor root and a smaller sensory root (the intermediate nerve):
The intermediate nerve contains the SA fibers for taste, the parasympathetic GVE fibers, and the GSA fibers.
The larger motor root contains the BE fibers.
The motor and sensory roots cross the posterior cranial fossa and leave the cranial cavity through the internal acoustic meatus (Fig. 8.53). After entering the facial canal in the petrous part of the temporal bone, the two roots fuse and form the facial nerve [VII]. Near this point the nerve enlarges as the geniculate ganglion, which is similar to a spinal ganglion containing cell bodies for sensory neurons.