The anterior two-thirds of the tongue differ from the posterior one-third of the tongue by its special visceral afferent (SVA; taste) innervation. The perikarya of neurons providing the sensation of taste in the anterior two-thirds of the tongue are found in which of the following?
(A) geniculate ganglion
(B) otic ganglion
© pterygopalatine (sphenopalatine) ganglion
(D) submandibular ganglion
(E) trigeminal (gasserian) ganglion
Explanation
(A) SVA (taste) fibers have their perikarya in the geniculate ganglion located in the petrous portion of the temporal bone. These neurons project their axons to the gustatory nucleus in the brainstem. The otic ganglion (choice B) receives preganglionic parasympathetic fibers originating from the inferior salivatory nucleus by way of the ninth cranial (glossopharyngeal) nerve. In turn, it projects postganglionic parasympathetic fibers to the parotid salivary gland. The pterygopalatine (sphenopalatine) ganglion (choice C) is also a parasympathetic ganglion, which receives preganglionic fibers from the superior salivatory nucleus by way of the ninth cranial (glossopharyngeal) nerve. In turn, it sends postganglionic parasympathetic fibers to the lacrimal gland and mucous glands in the nose. The submandibular ganglion (choice D) receives preganglionic parasympathetic fibers from the chorda tympani, a branch of the nervus intermedius which runs with the seventh cranial nerve. It innervates the submandibular and sublingual salivary glands. The trigeminal (gasserian) ganglion (choice E) receives sensations from the face, mucosa, cornea, teeth, gum, palate, and the anterior two-thirds of the tongue. It sends projections to the principal sensory and spinal trigeminal nuclei in the brainstem.