A ringlike muscle that controls a natural orifice.
A circular band of muscle which surrounds an opening or passage in the body, especially the anus, and can narrow or close the opening or passage by contracting.
A muscle, surrounding a body opening or vessel, that can contract and close that opening.
Circular band of muscle that constricts or closes an opening in the body (e.g., pyloric sphincter).
A muscle that encircles a duct or tube in such a manner that constriction closes the orifice or lumen.
A ring of muscle fibers that narrows a passage or closes an orifice. For example, sphincters control the opening and closing of the bladder and anus. A sphincter acts as a valve, regulating inflow or outflow. A sphincter can function automatically or can be partly under voluntary control, as with the bladder.
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 sphincter) and at the opening between the stomach and duodenum (pyloric sphincter).
A circular muscle which surrounds the opening from an organ, and, by maintaining a constant state of moderate urinary and rectum, and in certain nervous diseases their action is interfered with, so that the power to relax or to keep moderately contracted is lost, resulting in retention or incontinence of the evacuation.
A circular muscle constricting an orifice. In normal tonic condition, it closes the orifice, i.e., the muscle must relax to allow the orifice to open.
A ring-shaped muscle that relaxes or tightens to open or close a passage or opening in the body. Examples are the anal sphincter (around the opening of the anus) and the pyloric sphincter (at the lower opening of the stomach).
A circular band of muscle fibers that tightens or closes a natural opening of the body, such as the external anal sphincter, which closes the anus, and the internal and external urinary sphincters, which close the urinary canal.
The circular muscle that surrounds the digestive tract’s tube and serves as a functional valve is known as the sphincter.
A circular band of muscular tissue positioned between the bladder and the urethra, responsible for the closure of the urethral passage.
A circular band of muscle encircling a natural aperture or passageway in the body, responsible for controlling the inward or outward flow, as seen in the anal sphincter.