The tongue is our primary organ of taste, plays a key role in
our ability to speak, and helps keep our teeth clean. [1]
On average, the human tongue has 3,000–10,000 taste
buds [2]
which are involved in detecting the 5 known elements of taste
perception: salty, sour, bitter, sweet and umami (savory). [1]
These tastes can be detected by any area of the tongue. [1]
There is some evidence for a sixth taste that senses fatty substances. [3]
Food dissolved in our saliva comes into contact with
taste receptors through taste pores in the tongue epithelium. These
receptors (located on the surface of the taste receptor cells that comprise the taste buds), are responsible for
sending information to the gustatory areas of the brain via cranial nerves. [4][5]
Taste buds are located on the back and front of the tongue; the roof, sides and back of the mouth, and in the throat. [6] Each taste bud contains 50 to 100 taste receptor cells. [7]
 |
| Taste receptors are present on the human tongue in papillae [1] |
As taste senses both harmful and beneficial things, all basic tastes are classified as either aversive or appetitive, depending upon the effect the things they sense have on our bodies. [8] Sweetness helps to identify energy-rich foods, while bitterness serves as a warning sign of poisons. [9]
The ventral tegmental area (VTA) dopamine system is
strongly associated with the reward system of the brain. Dopamine is released as
a result of rewarding experiences such as food, sex, and neutral stimuli that
become associated with them. [10]
Animals in which the VTA dopamine system has been rendered inactive do not seek food, and will starve to death if left to themselves, but if food is placed in their mouths they will consume it and show facial expressions indicative of pleasure. [10]
Taste perception fades with age: On average, people lose half their taste receptors by the time they turn 20. [11]
Not all animals can sense all tastes. [12]
In 2010, researchers found bitter taste receptors in
lung tissue, which cause airways to relax when a bitter substance is
encountered. They believe this may be exploited to treat asthma and chronic
obstructive pulmonary disease. [13]
The ability to detect bitter-tasting, toxic compounds
at low thresholds is considered to provide an important protective function. [14][15]
Amongst leaf-eating
primates, there is a tendency to prefer immature leaves, which tend to be
higher in protein and lower in fiber and toxins than mature leaves. [16]
Amongst humans, various food processing techniques are used worldwide to detoxify otherwise inedible foods and make them palatable. [17] Furthermore, the use of fire, changes in diet, and avoidance of toxins has led to neutral evolution in human bitter sensitivity. This has allowed several loss of function mutations that has led to a reduced sensory capacity towards bitterness in humans when compared to other species. [18]
A metallic taste may be caused by food and drink, certain medicines or amalgam dental fillings. Regarding the latter, it has been shown that the dissimilar metals used in dental work may produce a measurable current. [19]
Blood is considered by many people to have a metallic taste. [20]
A metallic taste in the mouth is also a symptom of various medical conditions. [20]
A supertaster is a person whose sense of taste is significantly more sensitive than average. The cause of this heightened response is likely, at least in part, due to an increased number of fungiform papillae. [21]
Patients with Addison's disease, pituitary insufficiency, or cystic fibrosis sometimes have a hyper-sensitivity to taste perception. [22]
The eight muscles of the human tongue are classified as either intrinsic or extrinsic. [1]
The main functions of the extrinsic muscles are
altering the tongue's position allowing for protrusion, retraction, and
side-to-side movement. [23]:991
The intrinsic muscles lengthen, shorten, curl and uncurl, flatten and round its surface. This provides shape, and helps facilitate speech, swallowing, and eating. [23]:991
 |
| A Punnett square for one of Mendel's pea plant experiments. |
Rolling the tongue into a tube shape is often
described as a dominant trait with simple Mendelian inheritance. [24]
However, a 1975 twin study found that identical twins
were no more likely than fraternal twins to both have the same phenotype for
tongue rolling. [25][26]
 |
| Cloverleaf tongue |
Cloverleaf tongue is the ability to fold the tongue in a certain configuration with multiple bends.
The average length of the human tongue is 10 cm
(4 in). [27]
The tip-of-the-tongue phenomenon, sometimes called presque vu, is the failure to retrieve a word from memory, combined with partial recall and the feeling that retrieval is imminent. [29] The phenomenon's name comes from the saying, "It's on the tip of my tongue." [30][31][32] The tip of the tongue phenomenon reveals that lexical access occurs in stages. [33][34]
In 2009, a farmer from Fabriano, Italy was convicted and fined by the country's highest court for sticking his tongue out at a neighbor with whom he had been arguing. Proof of the affront had been captured with a cell phone camera. [36]
A dog's tongue acts as a heat regulator. As a dog increases its exercise, the tongue will increase in size due to greater blood flow. The tongue hangs out of its mouth and the moisture on the tongue will work to cool the blood flow. [37][38]
Updates & Related
Food debris, desquamated epithelial cells and
bacteria often form a visible tongue coating. [28]
This coating has been identified as a major contributing factor in bad breath (halitosis).
[28]
The tip-of-the-tongue phenomenon, sometimes called presque vu, is the failure to retrieve a word from memory, combined with partial recall and the feeling that retrieval is imminent. [29] The phenomenon's name comes from the saying, "It's on the tip of my tongue." [30][31][32] The tip of the tongue phenomenon reveals that lexical access occurs in stages. [33][34]
In Tibet, sticking out one’s tongue is considered a
greeting. [35]
In 2009, a farmer from Fabriano, Italy was convicted and fined by the country's highest court for sticking his tongue out at a neighbor with whom he had been arguing. Proof of the affront had been captured with a cell phone camera. [36]
A dog's tongue acts as a heat regulator. As a dog increases its exercise, the tongue will increase in size due to greater blood flow. The tongue hangs out of its mouth and the moisture on the tongue will work to cool the blood flow. [37][38]
- Scientists turn tastes on and off by activating and silencing clusters of brain cells / psypost.org / November 21, 2015
- Why Is My Tongue White? 4 Weird Tongue Problems And Their Symptoms Medical Daily September 11, 2015
- The five basic tastes have sixth sibling: oleogustus ScienceNews July 31, 2015
- Tongue Tied? What Your Tongue's Appearance Can Tell You About Your Health Medical Daily, June 11, 2014
- Why Doesn't Your Tongue Get Infected When You Bite It? HowStuffWorks.com Accessed July 30, 2015
References & Resources
[1] http://en.wikipedia.org/wiki/Tongue
[2] Encyclopædia Britannica. 2009. Encyclopædia Britannica Online
[3] Laugerette F, Passilly-Degrace P, Patris B, et al. (November 2005). "CD36 involvement in orosensory detection of dietary lipids, spontaneous fat preference, and digestive secretions". The Journal of Clinical Investigation 115 (11): 3177–84. doi:10.1172/JCI25299. PMC 1265871. PMID 16276419.
[4] http://en.wikipedia.org/wiki/Taste_bud
[5] Kobayashi, Masayuki (2006). "Functional Organization of the Human Gustatory Cortex". J. Oral Biosci 48 (4): 244–260. doi:10.1016/S1349-0079(06)80007-1.
[6] Boron, W.F., E.L. Boulpaep. 2003. Medical Physiology. 1st ed. Elsevier Science USA.
[7] http://en.wikipedia.org/wiki/Taste
[8] Why do two great tastes sometimes not taste great together? scientificamerican.com. Dr. Tim Jacob, Cardiff University. May 22, 2009.
[9] Miller, Greg (2 September 2011). "Sweet here, salty there: Evidence of a taste map in the mammilian brain.". Science 333 (6047): 1213. doi:10.1126/science.333.6047.1213.
[10] Arias-Carrión O, Pöppel E (2007). "Dopamine, learning and reward-seeking behavior". Act Neurobiol Exp 67 (4): 481–488.
[11] Schacter, Daniel (2009). Psychology Second Edition. United States of America: Worth Publishers. p. 169. ISBN 978-1-4292-3719-2.
[12] Scully, Simone M. "The Animals That Taste Only Saltiness". Nautilus.
[13] http://umm.edu/news-and-events/news-releases/2010/when-bad-tastes-good-discovery-of-taste-receptors-in-the-lungs-could-help-people-with-asthma-breathe-easier
[14] Guyton, Arthur C. (1991) Textbook of Medical Physiology. (8th ed). Philadelphia: W.B. Saunders
[15] Glendinning, J. I. (1994). "Is the bitter rejection response always adaptive?". Physiol Behav 56 (6): 1217–1227. doi:10.1016/0031-9384(94)90369-7. PMID 7878094.
[16] Jones, S., Martin, R., & Pilbeam, D. (1994) The Cambridge Encyclopedia of Human Evolution. Cambridge: Cambridge University Press
[17] Johns, T. (1990). With Bitter Herbs They Shall Eat It: Chemical ecology and the origins of human diet and medicine. Tucson: University of Arizona Press
[18] Wang, X. (2004). Relaxation Of Selective Constraint And Loss Of Function In The Evolution Of Human Bitter Taste Receptor Genes. Human Molecular Genetics, 13(21), 2671-2678.
[19] "Is there a Battery in your Mouth?". www.toothbody.com.
[20] Does Anxiety Cause a Metallic Taste in Your Mouth?, Calm Clinic. .
[21] Bartoshuk L. M., Duffy V. B. et al. (1994). "PTC/PROP tasting: anatomy, psychophysics, and sex effects." 1994". Physiol Behav 56 (6): 1165–71. doi:10.1016/0031-9384(94)90361-1. PMID 7878086.
[22] Walker, H. Kenneth (1990). "Clinical Methods: The History, Physical, and Laboratory Examinations". Retrieved 1 May 2014.
[23] Drake, Richard L.; Vogl, Wayne; Tibbitts, Adam W.M. Mitchell; illustrations by Richard; Richardson, Paul (2005). Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. ISBN 978-0-8089-2306-0.
[24] AP Biology Lab, Edwards-Knox Central School, Russel, NY
[25] Discovery Online, The Skinny On... Tongue Rolling
[26] Omim - Tongue Curling, Folding, Or Rolling
[27] Kerrod, Robin (1997). MacMillan's Encyclopedia of Science 6. Macmillan Publishing Company, Inc. ISBN 0-02-864558-8.
[28] (editors) Newman MG, Takei HH, Klokkevold PR, Carranza FA (2012). Carranza's clinical periodontology (11th ed.). St. Louis, Mo.: Elsevier/Saunders. pp. 84–96. ISBN 978-1-4377-0416-7.
[29] Brown, AS. (Mar 1991). "A review of the tip-of-the-tongue experience.". Psychological Bulletin 109 (2): 204–23. doi:10.1037/0033-2909.109.2.204. PMID 2034750.
[30] Schwartz, BL. (Sep 1999). "Sparkling at the end of the tongue: the etiology of tip-of-the-tongue phenomenology.". Psychonomic Bulletin & Review 6 (3): 379–93. doi:10.3758/bf03210827. PMID 12198776.
[31] Brown, Roger; McNeill, David (1966). "The "tip of the tongue" phenomenon". Journal of Verbal Learning and Verbal Behavior 5 (4): 325–337. doi:10.1016/S0022-5371(66)80040-3.
[32] Rastle, Kathleen G.; Burke, Deborah M. (1996). "Priming the Tip of the Tongue: Effects of Prior Processing on Word Retrieval in Young and Older Adults". Journal of Memory and Language 35 (4): 586–605. doi:10.1006/jmla.1996.0031.
[33] Beattie, G.; Coughlan, J. (Feb 1999). "An experimental investigation of the role of iconic gestures in lexical access using the tip-of-the-tongue phenomenon.". Br J Psychol 90 (1): 35–56. doi:10.1348/000712699161251. PMID 10085545.
[34] Schwartz, BL.; Metcalfe, J. (Jul 2011). "Tip-of-the-tongue (TOT) states: retrieval, behavior, and experience.". Mem Cognit 39 (5): 737–49. doi:10.3758/s13421-010-0066-8. PMID 21264637.
[35] Bhuchung K Tsering (27 December 2007). "Tibetan culture in the 21st century".
[36] Sticking out your tongue ruled illegal
[37] A dog's tongue
[38] Krönert, H.; Pleschka, K. (January 1976). "Lingual blood flow and its hypothalamic control in the dog during panting". Pflügers Archiv European Journal of Physiology 367 (1): 25–31. doi:10.1007/BF00583652. ISSN 0031-6768.
http://en.wikipedia.org/wiki/Dopamine
http://en.wikipedia.org/wiki/Tip_of_the_tongue
http://en.wikipedia.org/wiki/Tongue_rolling http://en.wikipedia.org/wiki/Gustatory_cortex
http://en.wikipedia.org/wiki/Mendelian_inheritance
[2] Encyclopædia Britannica. 2009. Encyclopædia Britannica Online
[3] Laugerette F, Passilly-Degrace P, Patris B, et al. (November 2005). "CD36 involvement in orosensory detection of dietary lipids, spontaneous fat preference, and digestive secretions". The Journal of Clinical Investigation 115 (11): 3177–84. doi:10.1172/JCI25299. PMC 1265871. PMID 16276419.
[4] http://en.wikipedia.org/wiki/Taste_bud
[5] Kobayashi, Masayuki (2006). "Functional Organization of the Human Gustatory Cortex". J. Oral Biosci 48 (4): 244–260. doi:10.1016/S1349-0079(06)80007-1.
[6] Boron, W.F., E.L. Boulpaep. 2003. Medical Physiology. 1st ed. Elsevier Science USA.
[7] http://en.wikipedia.org/wiki/Taste
[8] Why do two great tastes sometimes not taste great together? scientificamerican.com. Dr. Tim Jacob, Cardiff University. May 22, 2009.
[9] Miller, Greg (2 September 2011). "Sweet here, salty there: Evidence of a taste map in the mammilian brain.". Science 333 (6047): 1213. doi:10.1126/science.333.6047.1213.
[10] Arias-Carrión O, Pöppel E (2007). "Dopamine, learning and reward-seeking behavior". Act Neurobiol Exp 67 (4): 481–488.
[11] Schacter, Daniel (2009). Psychology Second Edition. United States of America: Worth Publishers. p. 169. ISBN 978-1-4292-3719-2.
[12] Scully, Simone M. "The Animals That Taste Only Saltiness". Nautilus.
[13] http://umm.edu/news-and-events/news-releases/2010/when-bad-tastes-good-discovery-of-taste-receptors-in-the-lungs-could-help-people-with-asthma-breathe-easier
[14] Guyton, Arthur C. (1991) Textbook of Medical Physiology. (8th ed). Philadelphia: W.B. Saunders
[15] Glendinning, J. I. (1994). "Is the bitter rejection response always adaptive?". Physiol Behav 56 (6): 1217–1227. doi:10.1016/0031-9384(94)90369-7. PMID 7878094.
[16] Jones, S., Martin, R., & Pilbeam, D. (1994) The Cambridge Encyclopedia of Human Evolution. Cambridge: Cambridge University Press
[17] Johns, T. (1990). With Bitter Herbs They Shall Eat It: Chemical ecology and the origins of human diet and medicine. Tucson: University of Arizona Press
[18] Wang, X. (2004). Relaxation Of Selective Constraint And Loss Of Function In The Evolution Of Human Bitter Taste Receptor Genes. Human Molecular Genetics, 13(21), 2671-2678.
[19] "Is there a Battery in your Mouth?". www.toothbody.com.
[20] Does Anxiety Cause a Metallic Taste in Your Mouth?, Calm Clinic. .
[21] Bartoshuk L. M., Duffy V. B. et al. (1994). "PTC/PROP tasting: anatomy, psychophysics, and sex effects." 1994". Physiol Behav 56 (6): 1165–71. doi:10.1016/0031-9384(94)90361-1. PMID 7878086.
[22] Walker, H. Kenneth (1990). "Clinical Methods: The History, Physical, and Laboratory Examinations". Retrieved 1 May 2014.
[23] Drake, Richard L.; Vogl, Wayne; Tibbitts, Adam W.M. Mitchell; illustrations by Richard; Richardson, Paul (2005). Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. ISBN 978-0-8089-2306-0.
[24] AP Biology Lab, Edwards-Knox Central School, Russel, NY
[25] Discovery Online, The Skinny On... Tongue Rolling
[26] Omim - Tongue Curling, Folding, Or Rolling
[27] Kerrod, Robin (1997). MacMillan's Encyclopedia of Science 6. Macmillan Publishing Company, Inc. ISBN 0-02-864558-8.
[28] (editors) Newman MG, Takei HH, Klokkevold PR, Carranza FA (2012). Carranza's clinical periodontology (11th ed.). St. Louis, Mo.: Elsevier/Saunders. pp. 84–96. ISBN 978-1-4377-0416-7.
[29] Brown, AS. (Mar 1991). "A review of the tip-of-the-tongue experience.". Psychological Bulletin 109 (2): 204–23. doi:10.1037/0033-2909.109.2.204. PMID 2034750.
[30] Schwartz, BL. (Sep 1999). "Sparkling at the end of the tongue: the etiology of tip-of-the-tongue phenomenology.". Psychonomic Bulletin & Review 6 (3): 379–93. doi:10.3758/bf03210827. PMID 12198776.
[31] Brown, Roger; McNeill, David (1966). "The "tip of the tongue" phenomenon". Journal of Verbal Learning and Verbal Behavior 5 (4): 325–337. doi:10.1016/S0022-5371(66)80040-3.
[32] Rastle, Kathleen G.; Burke, Deborah M. (1996). "Priming the Tip of the Tongue: Effects of Prior Processing on Word Retrieval in Young and Older Adults". Journal of Memory and Language 35 (4): 586–605. doi:10.1006/jmla.1996.0031.
[33] Beattie, G.; Coughlan, J. (Feb 1999). "An experimental investigation of the role of iconic gestures in lexical access using the tip-of-the-tongue phenomenon.". Br J Psychol 90 (1): 35–56. doi:10.1348/000712699161251. PMID 10085545.
[34] Schwartz, BL.; Metcalfe, J. (Jul 2011). "Tip-of-the-tongue (TOT) states: retrieval, behavior, and experience.". Mem Cognit 39 (5): 737–49. doi:10.3758/s13421-010-0066-8. PMID 21264637.
[35] Bhuchung K Tsering (27 December 2007). "Tibetan culture in the 21st century".
[36] Sticking out your tongue ruled illegal
[37] A dog's tongue
[38] Krönert, H.; Pleschka, K. (January 1976). "Lingual blood flow and its hypothalamic control in the dog during panting". Pflügers Archiv European Journal of Physiology 367 (1): 25–31. doi:10.1007/BF00583652. ISSN 0031-6768.
http://en.wikipedia.org/wiki/Dopamine
http://en.wikipedia.org/wiki/Tip_of_the_tongue
http://en.wikipedia.org/wiki/Tongue_rolling http://en.wikipedia.org/wiki/Gustatory_cortex
http://en.wikipedia.org/wiki/Mendelian_inheritance
Image Credits
"1402 The Tongue" by OpenStax College - Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013.. Licensed under Creative Commons Attribution 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:1402_The_Tongue.jpg#mediaviewer/File:1402_The_Tongue.jpg
"Lgive lashon" by אני (Transferred by חיים 7/Originally uploaded by צביה) - אני. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Lgive_lashon.JPG#mediaviewer/File:Lgive_lashon.JPG
"Punnett square mendel flowers" by Madprime - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Punnett_square_mendel_flowers.svg#mediaviewer/File:Punnett_square_mendel_flowers.svg
"4x curling tongue" by BigH22 - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0-2.5-2.0-1.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:4x_curling_tongue.jpg#mediaviewer/File:4x_curling_tongue.jpg
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