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Chapter 030. Disorders of Smell, Taste, and Hearing (Part 4)

Definitions Disturbances of the sense of taste may be categorized as total ageusia, total absence of gustatory function or inability to detect the qualities of sweet, salt, bitter, or sour; partial ageusia, ability to detect some but not all of the qualitative gustatory sensations; specific ageusia, inability to detect the taste quality of certain substances; total hypogeusia, decreased sensitivity to all tastants; partial hypogeusia, decreased sensitivity to some tastants; and dysgeusia or phantogeusia, distortion in the perception of a tastant, i.e., the perception of the wrong quality when a tastant is presented or the perception of a taste when. | Chapter 030. Disorders of Smell Taste and Hearing Part 4 Definitions Disturbances of the sense of taste may be categorized as total ageusia total absence of gustatory function or inability to detect the qualities of sweet salt bitter or sour partial ageusia ability to detect some but not all of the qualitative gustatory sensations specific ageusia inability to detect the taste quality of certain substances total hypogeusia decreased sensitivity to all tastants partial hypogeusia decreased sensitivity to some tastants and dysgeusia or phantogeusia distortion in the perception of a tastant i.e. the perception of the wrong quality when a tastant is presented or the perception of a taste when there has been no tastant ingested. Confusion between sour and bitter and less commonly between salty and bitter may represent a semantic misunderstanding or have a true pathophysiologic basis. It may be possible to differentiate between the loss of flavor recognition in patients with olfactory losses who complain of a loss of taste as well as smell by asking if they are able to taste sweetness in sodas saltiness in potato chips etc. Physiology of Taste The taste receptor cells are located in the taste buds spherical groups of cells arranged in a pattern resembling the segments of a citrus fruit Fig. 30-2 . At the surface the taste bud has a pore into which microvilli of the receptor cells project. Unlike the olfactory system the receptor cell is not the primary neuron. Instead gustatory afferent nerve fibers contact individual taste receptor cells. The papillae lie along the lateral margin and dorsum of the tongue at the junction of the dorsum and the base of the tongue and in the palate epiglottis larynx and esophagus. Figure 30-2 Taste. A. The taste buds of the anterior two-thirds of the tongue are innervated by the gustatory fibers that travel in a branch of the facial nerve VII called the chorda tympani. The taste buds of the posterior third of the tongue are innervated by .