In man the taste buds are found only in the mouth and are abundant in the tongue. They are distributed over the dorsal and under surface of of the tongue, on the laryngeal surface of the epiglottis, pharynx and on the cheek.
Each taste bud occupies the entire thickness of the epithelium. There is an opening on its free surface known as the pore canal. Taste buds are numerous at birth and their number decreases with age.
Taste sensation and disribution of taste cells :-
There are four primary or fundamental tastes. They are sweet, sour, salt and bitter. Alkaline and metallic taste are also sometimes included.
Taste buds mediating the four primary taste are localized in certain regions on the tongue. The taste bud sensitive to bitter taste are at the back of the tongue. Those for sour tastes are on the lateral surface. Those mediating salt at the anterior part of the dorsum near the tip. The taste bud sensitive to sweet are near the tip. The taste bud in the palate respond to sour and bitter taste but have some sensitivity to sweet and salt. The pharynx and epiglottis are not sensitive to all four tastes. It is found that both sweet and salt are insensitive to taste in these regions.
Mechanism of Stimulation
Taste receptors are stimulated by substances in solution. The dissolved substances act on the microvilli of the taste receptors which project at the gustatory pore and sets up a generator potential to the receptor. This inturn activates the afferent nerve ending at the base of the receptor, producing a propagated action potential in the nerve. The mechanism of production of generator potential varies in different receptors of taste.