Taste buds contain the receptors for taste.
They are located around the small structures on the upper surface of the tongue, soft palate,
upper esophagus, the cheek, epiglottis, which are called papillae.
These structures are involved in detecting the five elements of taste perception: salty,
sour, bitter, sweet, and umami.
A popular myth assigns these different tastes to different regions of the tongue; in reality
these tastes can be detected by any area of the tongue.
Via small openings in the tongue epithelium, called taste pores, parts of the food dissolved
in saliva come into contact with taste receptors.
These are located on top of the taste receptor cells that constitute the taste buds.
The taste receptor cells send information detected by clusters of various receptors
and ion channels to the gustatory areas of the brain via the seventh, ninth and tenth
cranial nerves.
On average, the human tongue has 3,000–10,000 taste buds.
Types of papillae The majority of taste buds on the tongue sit
on raised protrusions of the tongue surface called papillae.
There are four types of lingual papillae present in the human tongue:
Fungiform papillae - as the name suggests, these are slightly mushroom-shaped if looked
at in longitudinal section.
These are present mostly at the dorsal surface of the tongue, as well as at the sides.
Innervated by facial nerve.
Filiform papillae - these are thin, long papillae "V"-shaped cones that don't contain taste
buds but are the most numerous.
These papillae are mechanical and not involved in gustation.
They are characterized by increased keratinization.
Foliate papillae - these are ridges and grooves towards the posterior part of the tongue found
at the lateral borders.
Innervated by facial nerve and glossopharyngeal nerve.
Circumvallate papillae - there are only about 10 to 14 of these papillae on most people,
and they are present at the back of the oral part of the tongue.
They are arranged in a circular-shaped row just in front of the sulcus terminalis of
the tongue.
They are associated with ducts of Von Ebner's glands, and are innervated by the glossopharyngeal
nerve.
Taste buds are only present in circumvalate, fungiform papillae and soft palate.
Salts, sweet, sour and umami tastes causes depolarization of the taste cells, although
different mechanisms are applied.
Bitter causes an internal release of Ca2+, no external Ca2+ is required.
The bud is formed by two kinds of cells: supporting cells and gustatory cells.
The supporting cells are mostly arranged like the staves of a cask, and form an outer envelope
for the bud.
Some, however, are found in the interior of the bud between the gustatory cells.
The gustatory cells, a chemoreceptor, occupy the central portion of the bud; they are spindle-shaped,
and each possesses a large spherical nucleus near the middle of the cell.
The peripheral end of the cell terminates at the gustatory pore in a fine hair filament,
the gustatory hair.
The central process passes toward the deep extremity of the bud, and there ends in single
or bifurcated varicosities.
The nerve fibrils after losing their medullary sheaths enter the taste bud, and end in fine
extremities between the gustatory cells; other nerve fibrils ramify between the supporting
cells and terminate in fine extremities; these, however, are believed to be nerves of ordinary
sensation and not gustatory.
The average life of a taste bud is 10 days.
See also Taste
Taste receptor Gustatory system
Tongue map Additional images
References
External links Taste Perception: Cracking the Code
Scientists Explore the Workings of Taste Buds from National Public Radio's Talk of the Nation,
July 22, 2005 http:kidshealth.orgtalktaste_buds.html For
kids about taste buds!
http:www.newser.com103744/your-lungs-have-their-own-taste-buds.html