Anatomical hierarchy

General Anatomy > Alimentary system > Large intestine > Anal canal > Internal anal sphincter

Translations

Description

Nerve: Pudendal nerve

Action: Keep the anal canal and anus closed, aids in the expulsion of the feces

Description:
The Sphincter ani internus (Internal sphincter ani) is a muscular ring which surrounds about 2.5 cm. of the anal canal; its inferior border is in contact with, but quite separate from, the Sphincter ani externus. It is about 5 mm. thick, and is formed by an aggregation of the involuntary circular fibers of the intestine. Its lower border is about 6 mm. from the orifice of the anus.
Actions.—Its action is entirely involuntary. It helps the Sphincter ani externus to occlude the anal aperture and aids in the expulsion of the feces.


Text by Antoine Micheau, MD - Copyright IMAIOS

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