sphincter

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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

(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.

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.

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]
References in periodicals archive ?
First, a semicircular incision was made matching the projection of the anal sphincter. The second U-shaped incision was made on the posterior commissure of the bulbospongiosus muscles (Figure 1).
In the distal anal canal, the IAS is thin; therefore, we measured the PBT, anterior anal sphincter defect and anal sphincter defect angle at the level of the mid-anal canal, which can be clearly delineated by the presence of the most prominent hypoechoic ring of the IAS.
The results of studies exploring the impact of vaginal delivery on anal canal anatomy in the absence of sphincter disruption are conflicting.
The operative management of anal fissure was aimed to cause permanent functional changes in the internal sphincter. It has been shown that the resting tone of internal anal sphincter is higher in patients of chronic anal fissure.
The anal fistula plug poses a lower risk of postoperative impairment of sphincter muscle function and other postoperative complications than the cutting setons and transanal mucosal advancement flap.
Despite success with slings in a select group of patients, i.e., those with low preoperative pad weights, appropriate external sphincter coaptation on preoperative cystoscopy, and no history of prior radiation or urethral surgery, there are many patients who do not fit these criteria and are better served with AUS.
A failed repair was considered present when there was wound dehiscence, sphincter disruption, rectovaginal fistula, and/or faecal incontinence.
However, one study showed the frequency of third and fourth degree perineal tears as 0.5%.7 Considering limited resources, we initiated local hands-on workshops using an experimental multiparous goat model for the repair of OASI to educate obstetricians and residents in perineal and anal sphincter anatomy and repair techniques of OASI.
There are actually two sphincters at the anus - one internal and one external.
Just before you urinate, the sphincter first relaxes and then, in reflex fashion the bladder muscle contracts, squeezing urine out through the urethra.