THE SENSE OF TASTE

Taste is regarded as a contact sense operating when it is in the contact with the source of taste. The receptive bases for the four basic taste qualities: sweet, sour, bitter, and salty, are the taste receptor cells. These taste receptor cells are located on taste buds (30 to 80 cells per taste bud) which detect stimuli dissolved in water, oil, or saliva. Because these receptors respond to chemicals in an aqueous solution they are called chemoreceptors. The taste buds are located on papillae which are nipple like elevations on the surface of the tongue, as well as on the mucosa of the pallate and areas of the throat. The human tongue contains three types of taste papillae: fungiform, foliated and vallate. There are a total of about 2000 taste buds with over half located on the vallate papillae. Filiform papillae are another type of papillae, yet do not contain any taste buds hence donÆt participate in taste sensation. The fungiform papillae are scattered over the entire surface of the tongue, but are most abundant along the sides of the tongue and the tip. The taste buds are located on the tops of these papillae, as illustrated by the diagram below. Vallate papillae form an inverted V shaped borderline at the back of the tongue with the taste buds located in the vallate side walls. The location of the taste buds in the foliate papillae are also in the side walls.

Location of Taste Buds

A Taste Bud

Each of the taste buds consists 40 to 60 epithelial cells of three types.

The first type of epithelial cell is the supporting cells that comprise most of the taste bud. These cells insulate the second type of cells, the gustatory or taste receptor cells. Basal cells are responsible for replacing taste receptor cells when they shed every 7 to 10 days(Marieb, E.N.).

Activation of the taste receptors is not fully understood. Long microvilli project from the tips of the taste receptor cells and extend through a taste pore to the surface of the epithelium where they are bathed by saliva. It is these microvilli that are the sensitive portions of the taste receptor cells in that they are assumed to bear chemical receptor sites to which taste molecules, dissolved in saliva, are to be bound. This initiates primary processes of taste. The taste receptors are secondary sensory cells in that they do not have axons to conduct impulses centrally. Their responses are transmitted by afferent fibers that form synapses near the bases of taste receptor cells. All the taste receptor cells in the same taste bud are connected by basal synapses to about 50 afferent taste fibers running toward the CNS, sending messages to the brain(Schmidt, R.F.). Refer to the above diagram.

Sensory Physiology Nancy L. DeVore

Updated 8/29/97. Send mail to Food Resource, Oregon State University, Corvallis, OR.