musculus sphincter ani internus

Thesaurus

Noun

1.

musculus sphincter ani internus - an internal ring of smooth muscle formed by circular fibers of the rectum involuntary muscle, smooth muscle - a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart) anal sphincter, musculus sphincter ani, sphincter ani - the sphincter muscle of the anus