The surface of the tongue is covered with various small bumps called papillae, which either distribute what has been ingested (filiform papillae) or contain the sensory taste (or gustatory) receptor cells (fungiform, circumvallate, and foliate papillae). Embedded within each taste-related papilla are the taste buds—clusters of 30 to 100 gustatory receptor cells.
Gustatory receptor cells extend finger-like projections called gustatory hairs (or microvilli) into a region known as the taste pore. Here, many of the cells contain receptors that detect different tastants—the molecules that can be tasted. The average number of taste buds varies significantly among individuals, with estimates ranging from 2,000-10,000 taste buds. Taste cells have a lifespan of about 10-14 days and are continually replaced. Thus, each taste bud contains taste cells at different stages of development.
Aside from the filiform papillae, which do not contain taste buds, the mushroom-shaped fungiform papillae are the most numerous. Fungiform papillae are predominantly located on the anterior two-thirds of the tongue and contain between one and eight taste buds each.
In contrast, the other two types of papillae—circumvallate and foliate—contain more than 100 taste buds per papilla. Circumvallate papillae, the largest type, are located at the back of the tongue in “V”-like formation. Nearby, on the sides of the tongue, are the foliate papillae.
The work of many scientists, including Collings, Yanagisawa, and colleagues, indicates that the five basic tastes can be perceived anywhere across the tongue. Thus, distinct tastes are not restricted to particular regions, as typically indicated on tongue maps.
