sphincter

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sphincter

Anatomy a ring of muscle surrounding the opening of a hollow organ or body and contracting to close it

Sphincter

 

a ringlike muscle that constricts to close a natural orifice such as the oral or anal opening, or to narrow the passage from one part of a hollow tubular organ to another, for example, from the stomach and bile duct to the duodenum and from the bladder to the urethra. The sphincter is always in a tonic state. The orbicular muscle of the iris is a sphincter. Some sphincters consist of striated muscle and others of smooth muscle innervated by the autonomic nervous system.

sphincter

[′sfiŋk·tər]
(anatomy)
A muscle that surrounds and functions to close an orifice.
References in periodicals archive ?
The antagonist activity of aripiprazole at 5-HT2A and alfa 1 receptors on detrusor muscle and internal bladder sphincter, respectively, might have contributed to enuresis in our case, although it had no noticeable anticholinergic effects.
In women, stress incontinence (involuntary loss of urine during physical activity such as sneezing or exercise) is usually caused by a weakening of the bladder sphincter and pelvic floor muscles.
Cauda equina syndrome is characterized by lower extremity weakness or paralysis, bowel or bladder sphincter dysfunction, and saddle anesthesia.