What is the role of the gustatory system in the pathophysiology of taste and smell disorders?

Updated: Dec 11, 2018
  • Author: Eric H Holbrook, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Answer

Taste perception is mediated by individual taste buds, with 50-100 tightly packed cells in each bud. Taste buds are made up of modified epithelial cells and chemical receptor cells; however, the receptor cells are not direct neurons as in the olfactory system. Taste bud cells are classified into cell types I-IV and include supporting cells (types I and II), receptor cells (type III), and basal progenitor cells (type IV). [7] These cells have a life span of approximately 10 days and arise continuously from the underlying basal cell layer in a process of constant turnover, similar to that of olfactory receptor neurons. Any bud may contain any of the receptor cells necessary to identify each different taste.

Afferent nerve branches making synaptic contact with receptor cells penetrate the base of the taste bud. Taste buds occupy papillae, which are projections embedded in the tongue epithelium. A single nerve fiber innervates multiple taste papillae, and the nerve contact exerts trophic influences on the epithelium.

The specificity of the gustatory receptor cells is determined by the epithelium in which it resides, not by the particular nerve innervating the bud. A single fiber in the chorda tympani may respond to multiple types of tastes, some tastes more than others. This ability of single nerve fibers to respond to multiple types of stimuli is referred to as broad tuning, and it is shared by the olfactory system.


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