a circular band of voluntary or involuntary muscle that encircles an orifice of the body or one of its hollow organs.
(anatomy) a ring of muscle surrounding the opening of a hollow organ or body and contracting to close it
sphincter sphinc·ter (sfĭngk’tər)
A ringlike muscle that normally maintains constriction of a body passage or orifice and that relaxes as required by normal physiological functioning. Also called anatomical sphincter.
sphinc’ter·al or sphinc·ter’ic (-těr’ĭk) adj.
A ring-shaped muscle that encircles an opening or passage in the body. The opening and closing of the anus is controlled by contraction and relaxation of a sphincter, as is the opening that leads to the stomach from the esophagus.
sphincteralgia sphinc·ter·al·gi·a (sfĭngk’tə-rāl’jē-ə, -jə) n. Pain in the muscles of the anal sphincter.
sphincterectomy sphinc·ter·ec·to·my (sfĭngk’tə-rěk’tə-mē) n. Excision of a portion of the pupillary border of the iris. Excision of a sphincter muscle.
sphincterismus sphinc·ter·is·mus (sfĭngk’tə-rĭz’məs) n. Spasmodic contraction of the muscles of the anal sphincter.
sphincteritis sphinc·ter·i·tis (sfĭngk’tə-rī’tĭs) n. Inflammation of a sphincter.