Fibers enter the brain stem with the intermediate nerve and synapse in the nucleus of the solitary tract. The primary sensory neurons are in the geniculate ganglion and gather sensory information via the greater petrosal nerve from the nasal cavity, part of the soft palate, and the sinus cavities. The general visceral afferent (GVA) component is very small. GVE preganglionic neurons are located in the superior salivatory nucleus in the brain stem. The lingual nerve reaches the submandibular and sublingual glands where the GVE fibers cause vasodilation and stimulate secretion. The chorda tympani synapses in the submandibular ganglion and later with GVE travels as the lingual nerve, a branch of the mandibular nerve. These postganglionic fibers cause vasodilation and cause secretion in the lacrimal gland. The greater petrosal nerve supplies the lacrimal gland by giving branches to the zygomatic branch of the maxillary nerve, which later travels as the lacrimal nerve to the lacrimal gland. After synapsing in the pterygopalatine ganglion, the greater petrosal nerve provides postganglionic parasympathetic innervation to nasal, oral, and palatine glands. General visceral efferent (GVE) fibers (parasympathetic preganglionic motor fibers) leave the facial nerve as the greater petrosal nerve and the chorda tympani nerve. The neurons of these fibers are localized in the facial nucleus in the caudal pontine tegmentum. Their function is to innervate the muscles of facial expression, the stapedius muscle, the stylohyoid muscle, and the posterior belly of the digastric muscle. Special visceral efferent (SVE) fibers (branchiomotor) are a major component of the facial nerve. The facial nerve also carries taste sensation from the anterior two-thirds of the tongue. The sensory component provides innervation to the external auditory meatus, the tympanic membrane, and the pinna of the ear. Parasympathetic fibers go to the ganglia that supply glands in the oral cavity and the lacrimal gland. Motor axons innervate the muscles of facial expression and the stapedius muscle. The facial nerve carries both motor and sensory fibers.
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