Full Title: (Canine) Anal Sphincter Muscle
Author: Mariana Elaine Purcell
Date of Publication: March 5, 2012
Research Paper Text:
A sphincter muscle is a structure or circular muscle (circular in form) that normally maintains constriction of a natural body passage or orifice, which relaxes as required by normal function.
The External anal sphincter muscle is named this because it is located in the anus and is a circular muscle that normally maintains constriction. The job of the anal sphincter muscle is to constrict and maintain continence. This muscle helps the contraction of waste to be secreted from the body. It is voluntarily used by pressure and allows for the storage of wastes to exit the body. The size of this muscle depends on the dog. The size can be anywhere from 1cm to 2cm in diameter, up to a few cm.
There is no insertion/attachment site on a sphincter muscle. The whole muscle is basically attached to the Levator ani, which is the broad muscle attaching to the pelvis and making up the perineum. The anal sphincter is just muscle tissue so there is no tendon or ligaments either. The blood supply and innervations come from the external obturator artery, vein and nerve.