Taste bud
Encyclopedia
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
and epiglottis
, which are called papillae. These structures are involved in detecting the five (known) elements of taste perception: salty
, sour, bitter, sweet, and umami
. Via small openings in the tongue epithelium, called taste pores, parts of the food dissolved in saliva
come into contact with taste receptor
s. 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 2,000–8,000 taste buds.
It is generally accepted that there are five taste sensations:
, and its neck opening, the gustatory pore, between the cells of the epithelium.
The bud is formed by two kinds of cells: supporting cells and gustatory cells.
The supporting (sustentacular) 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 (taste) 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. Some early experimental studies (Kirk and Grills, 1992)it was shown that subjects who were genetically predisposed to baldness were found to be 78% more likely to experience taste loss sensations in 5 out of 5 taste trials.It was hypothesized that this was due to 'balding' of the tongue.
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.
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
, soft palate
Soft palate
The soft palate is the soft tissue constituting the back of the roof of the mouth. The soft palate is distinguished from the hard palate at the front of the mouth in that it does not contain bone....
, upper esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
and epiglottis
Epiglottis
The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term, like tonsils, is often incorrectly used to refer to the uvula...
, which are called papillae. These structures are involved in detecting the five (known) elements of taste perception: salty
Salty
Salty may refer to the following:* salt* Saltiness, one of the five basic tastes* salt * salience* LondonerFictional characters:* Salty the Seal, character in Disney's Pluto cartoons...
, sour, bitter, sweet, and umami
Umami
Umami , popularly referred to as savoriness, is one of the five basic tastes together with sweet, sour, bitter, and salty.-Etymology:Umami is a loanword from the Japanese meaning "pleasant savory taste". This particular writing was chosen by Professor Kikunae Ikeda from umai "delicious" and mi ...
. Via small openings in the tongue epithelium, called taste pores, parts of the food dissolved in saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
come into contact with taste receptor
Taste receptor
A Taste receptor is a type of receptor which facilitates the sensation of taste.Examples include TAS2R16 and TAS2R38.They are divided into two families:* Type 1, sweet, first characterized in 2001: –...
s. 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 2,000–8,000 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 papillae present in the human tongue:- Fungiform papillae - as the name suggests, these are slightly mushroomMushroomA mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi that...
-shaped if looked at in longitudinal section. These are present mostly at the apex (tip) 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 papillaeFoliate papillaeTaste-buds, the end-organs of the gustatory sense, are scattered over the mucous membrane of the mouth and tongue at irregular intervals. They occur especially in the sides of the vallate papillae. There is a localized area at the side of the base of the tongue, the foliate papillae, in which they...
- these are ridges and grooves towards the posterior part of the roof of the mouth found on lateral margins. Innervated by facial nerveFacial nerveThe facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
(anterior papillae) and glossopharyngeal nerveGlossopharyngeal nerveThe glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves . It exits the brainstem out from the sides of the upper medulla, just rostral to the vagus nerve...
(posterior papillae). - Circumvallate papillaeCircumvallate papillaeThe circumvallate papillae are dome-shaped structures on the human tongue that vary in number from eight to twelve....
- 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 tongueTerminal sulcus (tongue)The dorsum of the tongue is convex and marked by a median sulcus, which divides it into symmetrical halves; this sulcus ends about 2.5 cm. from the root of the organ, in a depression called the foramen cecum, from which a shallow groove, the terminal sulcus, runs laterally and forward on either...
. They are associated with ducts of Von Ebner's glandsVon Ebner's glandsVon Ebner's glands are named after Anton Gilbert Victor von Ebner, Ritter von Rosenstein, who was an Austrian histologist....
, and are innervated by the glossopharyngeal nerve.
It is generally accepted that there are five taste sensations:
- Sweet, Bitter, and Savory (now sometimes called Umami), which work with a signal through a G protein-coupled receptorG protein-coupled receptorG protein-coupled receptors , also known as seven-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors , comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal...
. - Salty, and Sour, which work with ion channelIon channelIon channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...
s.
Localization of taste and the specious "tongue map"
Contrary to popular understanding that different tastes map to different areas of the tongue, taste qualities are found in all areas of the tongue, although some regions are more sensitive than others.Structure of taste buds
Each taste bud is flask-like in shape, its broad base resting on the coriumCorium
Corium may refer to:* Corium , the lava-like result of meltdown* Corium , an insect genus...
, and its neck opening, the gustatory pore, between the cells of the epithelium.
The bud is formed by two kinds of cells: supporting cells and gustatory cells.
The supporting (sustentacular) 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 (taste) 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. Some early experimental studies (Kirk and Grills, 1992)it was shown that subjects who were genetically predisposed to baldness were found to be 78% more likely to experience taste loss sensations in 5 out of 5 taste trials.It was hypothesized that this was due to 'balding' of the tongue.
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.
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.org/kid/talk/qa/taste_buds.html For kids about taste buds!
- http://www.newser.com/story/103744/your-lungs-have-their-own-taste-buds.html
- http://en.wikipedia.org/wiki/Taste_bud#Types_of_papillae