musculus sphincter ani internus

English Thesaurus

1. an internal ring of smooth muscle formed by circular fibers of the rectum (noun.body)

hypernym	:	involuntary muscle, smooth muscle,
definition	:	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) (noun.body)

part meronym	:	anal sphincter, musculus sphincter ani, sphincter ani,
definition	:	the sphincter muscle of the anus (noun.body)