sphincter

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Related to rectal sphincter: sphincter control

sphincter

 [sfingk´ter]
a circular muscle that constricts a passage or closes a natural orifice. When relaxed, a sphincter allows materials to pass through the opening. When contracted, it closes the opening. Four main sphincter muscles along the alimentary canal aid in digestion: the cardiac sphincter, the pyloric sphincter, and two anal sphincters. Other sphincters are found in the iris of the eye, the bile duct (sphincter of Oddi), the urinary tract, and elsewhere.
anal sphincter (sphincter a´ni) either of two sphincters (the internal and external anal sphincters) that open and close to control evacuation of feces from the anus.
cardiac sphincter a sphincter between the esophagus and the stomach, opening at the approach of food that can then be swept into the stomach by rhythmic peristaltic waves.
sphincter of Oddi a sheath of muscle fibers investing the associated bile and pancreatic passages as they traverse the wall of the duodenum.
pyloric sphincter a sphincter at the opening from the stomach into the duodenum; it is usually closed, opening only for a moment when a peristaltic wave passes over it.
urinary sphincter, artificial a fluid-filled system that surrounds the urethra with a silicone cuff that functions as a sphincter; a pump is in the scrotum and a fluid reservoir is in the abdomen. For urination, the pump's release valve is squeezed to allow the fluid to leave the urethral cuff and return to the reservoir; after urination is complete, the pump is squeezed and the fluid returns to the cuff to occlude the urethra.

sphinc·ter

(sfingk'tĕr), [TA]
A muscle that encircles a duct, tube, or orifice in such a way that its contraction constricts the lumen or orifice.
Synonym(s): musculus sphincter [TA], sphincter muscle [TA]
[G. sphinktēr, a band or lace]

sphincter

/sphinc·ter/ (sfingk´ter) [L.] a ringlike muscle which closes a natural orifice or passage.sphinc´teralsphincter´ic
anal sphincter , sphincter a´ni sphincter muscle of anus (external or internal).
cardiac sphincter , cardioesophageal sphincter muscle fibers about the opening of the esophagus into the stomach.
external sphincter of female urethra  external sphincter muscle of female urethra.
external sphincter of male urethra  external sphincter muscle of male urethra.
gastroesophageal sphincter  the terminal few centimeters of the esophagus, which prevents reflux of gastric contents into the esophagus.
hepatic sphincter  a thickened portion of the muscular coat of the hepatic veins near their entrance into the inferior vena cava.
internal sphincter of urethra  internal sphincter muscle of urethra.
O'Beirne's sphincter  a band of muscle at the junction of the sigmoid colon and rectum.
sphincter of Oddi  the sheath of muscle fibers investing the associated bile and pancreatic passages as they traverse the wall of the duodenum.
pharyngoesophageal sphincter  a region of higher muscular tone at the junction of the pharynx and esophagus, which is involved in movements of swallowing.
precapillary sphincter  a smooth muscle fiber encircling a true capillary where it originates from the arterial capillary, which can open and close the capillary entrance.
pyloric sphincter  see under muscle.
rectal sphincter  an incomplete band or thickening of the muscle fibers in the rectum a few inches above the anus in the upper part of the rectal ampulla.
tubal sphincter  an encircling band of muscle fibers at the junction of the uterine tube and the uterus.
vesical sphincter  internal sphincter muscle of urethra.

sphincter

(sfĭngk′tər)
n.
A ringlike muscle that normally maintains constriction of a body passage or orifice and that relaxes as required by normal physiological functioning.

sphinc′ter·al adj.

sphincter

[sfingk′tər]
Etymology: Gk, sphingein, to bind
a circular band of muscle fibers that constricts a passage or closes a natural opening in the body, such as the hepatic sphincter in the muscular coat of the hepatic veins near their union with the superior vena cava, and the external anal sphincter, which closes the anus.

sphinc·ter

(sfingk'tĕr) [TA]
A muscle that encircles a duct, tube, or orifice in such a way that its contraction constricts the lumen or orifice; it is the closing component of a pylorus (the outer component is the musculus dilatator).
Synonym(s): sphincter muscle.
[G. sphinktēr, a band or lace]

sphincter

A muscle ring, or local thickening of the muscle coat, surrounding a tubular passage or opening in the body. When a sphincter contracts it narrows or closes off the passageway.

sphincter

a ring of muscle surrounding a tube or the opening to a tube that controls the size of the aperture it surrounds and, thus, the movement through the tube;examples are pyloric and anal sphincters.Sphincter muscles are unusual in that they are normally contracted and only occasionally relax.

Sphincter

A circular band of muscle that surrounds and encloses an opening to the body or to one of its hollow organs. Damage to the sphincter surrounding the anus can cause fecal incontinence.

sphincter

circular muscle; contraction reduces the diameter of an orifice/lumen

sphinc·ter

(sfingk'tĕr) [TA]
Muscle that encircles a duct, tube, or orifice in such a way that its contraction constricts the lumen or orifice.
[G. sphinktēr, a band or lace]

sphincter (sfingk´tər),

n a circular band of muscle fibers that constricts a passage or closes a natural opening in the body.

sphincter

a circular muscle that constricts a passage or closes a natural orifice. When relaxed, a sphincter allows materials to pass through the opening. When contracted, it closes the opening. The principal abnormalities relate to function. Failure to open may be because of spasm or achalasia, due usually to failure of parasympathetic nerve supply. Failure to close usually due to absence of sympathetic nerve supply. The important sphincters are the anal, ileal, pharyngoesophageal, pupillary, pyloric, reticulo-omasal, teat, urethral, vaginal and vesical.

cardiac sphincter
the functional sphincter at the gastric end of the esophagus.
sphincter control
is by the autonomic nervous system.
esophageal sphincter
see cardiac sphincter.
sphincter of Oddi
bile duct sphincter.
pupillary sphincter
a ring of smooth muscle around the pupillary border of the iris.