19.2:
The Tongue and Taste Buds
The surface of our tongue is covered in hundreds of tiny bumps called papillae. One type, filiform, simply provides the friction needed to move food around.
Within other papillae—fungiform, circumvallate, and foliate—are numerous taste buds—clusters of gustatory cells. Each papilla increases the surface area, which is important for taste intensity.
At the very tip of every taste bud, protruding through a pore, are microvilli—hair-like extensions that contain different chemoreceptors.
When dissolved molecules called tastants bind to specific receptors, the cell is stimulated and activates nearby nerve endings. The nerves then pass the signal on to the brain for a particular perception of flavor.
19.2:
The Tongue and Taste Buds
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.
Different Types of Taste Papillae
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 Myth of the Tongue’s Taste Map
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.
Suggested Reading
Roper, Stephen D., and Nirupa Chaudhari. “Taste Buds: Cells, Signals and Synapses.” Nature Reviews. Neuroscience 18, no. 8 (August 2017): 485–97. [Source]