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|Noun||1.||anal sphincter - the sphincter muscle of the anus|
anus - the excretory opening at the end of the alimentary canal
anatomical sphincter, sphincter, sphincter muscle - a ring of muscle that contracts to close an opening
musculus sphincter ani externus - an external ring of striated muscle surrounding the anus
musculus sphincter ani internus - an internal ring of smooth muscle formed by circular fibers of the rectum