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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
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.
[G. sphinktēr, a band or lace]
Farlex Partner Medical Dictionary © Farlex 2012
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.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
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]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
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.Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
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.Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
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.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
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]
Medical Dictionary for the Dental Professions © Farlex 2012