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sphincter
sphincter A band of muscle encircling one of the body's ‘tubes’, and so able to alter the ‘bore’ by contracting/relaxing. In the alimentary tract there are sphincters at the exit from the stomach, between the small and large intestine, and at the anus; another regulates the flow of bile and pancreatic juice into the duodenum. In the urogenital tract, there are sphincters at the exit from the bladder. They occur also in the walls of small arterial blood vessels, regulating the flow into the capillaries beyond, according to local requirements. Those which assist retention of the excreta are partly under voluntary control; all the others, formed only of smooth muscle, are regulated by the autonomic nervous system; in general, sympathetic nerves constrict them; in the gut, parasympathetic nerves relax them. The thin sheet of circular muscle of the iris which constricts the pupil of the eye is also known as a sphincter — it is stimulated by parasympathetic nerves, in response to light and as part of accommodation for near vision.
Stuart Judge See alimentary system; autonomic nervous system; bladder. |
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COLIN BLAKEMORE and SHELIA JENNETT. "sphincter." The Oxford Companion to the Body. 2001. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. COLIN BLAKEMORE and SHELIA JENNETT. "sphincter." The Oxford Companion to the Body. 2001. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O128-sphincter.html COLIN BLAKEMORE and SHELIA JENNETT. "sphincter." The Oxford Companion to the Body. 2001. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O128-sphincter.html |
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sphincter
sphinc·ter / ˈsfingktər/ • n. Anat. a ring of muscle surrounding and serving to guard or close an opening or tube, such as the anus or the openings of the stomach. DERIVATIVES: sphinc·ter·al / -əl/ adj. sphinc·ter·ic / ˌsfingkˈterik/ adj. ORIGIN: late 16th cent.: via Latin from Greek sphinktēr, from sphingein ‘bind tight.’ |
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"sphincter." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. "sphincter." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O999-sphincter.html "sphincter." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-sphincter.html |
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sphincter
sphincter (sfink-ter) n. a specialized ring of muscle that surrounds an orifice. Contractions of the sphincter partly or completely close the orifice. Sphincters are found, for example, around the anus (anal s.) and at the openings between the stomach and the oesophagus (cardiac s.) and the duodenum (pyloric s.).
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"sphincter." A Dictionary of Nursing. 2008. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. "sphincter." A Dictionary of Nursing. 2008. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O62-sphincter.html "sphincter." A Dictionary of Nursing. 2008. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O62-sphincter.html |
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sphincter
sphincter A specialized muscle encircling an opening or orifice. Contraction of the sphincter tends to close the orifice. Examples are the anal sphincter (round the opening of the anus) and the pyloric sphincter (at the lower opening of the stomach).
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"sphincter." A Dictionary of Biology. 2004. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. "sphincter." A Dictionary of Biology. 2004. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O6-sphincter.html "sphincter." A Dictionary of Biology. 2004. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-sphincter.html |
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sphincter
sphincter Ring of muscle surrounding a body orifice which can open it or seal it off. Important sphincters include the pyloric sphincter in the stomach and the anal sphincter.
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"sphincter." World Encyclopedia. 2005. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. "sphincter." World Encyclopedia. 2005. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O142-sphincter.html "sphincter." World Encyclopedia. 2005. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-sphincter.html |
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sphincter
sphincter (anat.) muscular ring normally closing an orifice. XVI. — late L. — Gr. sphigktēr band, contractile muscle, f. sphíggein bind tight
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T. F. HOAD. "sphincter." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. T. F. HOAD. "sphincter." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O27-sphincter.html T. F. HOAD. "sphincter." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-sphincter.html |
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sphincter
sphincter
•bitter, committer, critter, embitter, emitter, fitter, flitter, fritter, glitter, gritter, hitter, jitter, knitter, litter, permitter, pitta, quitter, remitter, sitter, skitter, slitter, spitter, splitter, submitter, titter, transmitter, twitter, witter
•drifter, grifter, lifter, shifter, sifter, snifter, uplifter
•constrictor, contradictor, depicter, dicta, evictor, inflicter, predictor, victor
•filter, kilter, philtre (US philter), quilter, tilter
•Jacinta, midwinter, Minter, Pinta, Pinter, printer, splinter, sprinter, tinter, winter
•sphincter
•assister, ballista, bistre (US bister), blister, enlister, glister, lister, mister, resistor, Sandinista, sister, transistor, tryster, twister, vista
•trickster
•minster, spinster
•hipster, quipster, tipster
•cohabiter • arbiter • presbyter
•exhibitor, inhibitor, prohibiter
•Manchester • Chichester • Silchester
•Rochester • Colchester
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•auditor • Perdita • taffeta • shopfitter
•forfeiter • outfitter • counterfeiter
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•Alistair • weightlifter • filleter
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•diameter, heptameter, hexameter, parameter, pentameter, tetrameter
•Axminster • Westminster
•limiter, perimeter, scimitar, velocimeter
•accelerometer, anemometer, barometer, gasometer, geometer, manometer, micrometer, milometer, olfactometer, optometer, pedometer, photometer, pyrometer, speedometer, swingometer, tachometer, thermometer
•Kidderminster • janitor
•banister, canister
•primogenitor, progenitor, senator
•administer, maladminister, minister, sinister
•monitor • per capita • carpenter
•spanakopita • Jupiter • trumpeter
•character • barrister • ferreter
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•capacitor • ancestor • Exeter
•stepsister
•elicitor, solicitor
•babysitter • house-sitter • bullshitter
•competitor • catheter • harvester
•riveter • banqueter • non sequitur
•loquitur
•inquisitor, visitor
•compositor, expositor
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"sphincter." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. "sphincter." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O233-sphincter.html "sphincter." Oxford Dictionary of Rhymes. 2007. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O233-sphincter.html |
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