The anal canal is located within the anal triangle of the perineum between the right and left ischioanal fossae. It is the final segment of the gastrointestinal tract, around 4cm in length. The canal begins as a continuation of the rectum and passes inferoposteriorly to terminate at the anus. Except during defecation, the anal canal is collapsed by the internal and external anal sphincters to prevent the passage of faecal material.
External anal sphincter
Puborectalis muscle and External Anal Sphincter: a functional unit?
The external anal sphincter or sphincter ani externus is a flat plane of skeletal muscle fibers, elliptical in shape and intimately adherent to the skin surrounding the margin of the anus. In a considerable proportion of cases the fibers decussate in front of the anus, and are continuous with the superficial transverse perineal muscle. Posteriorly, they are not attached to the coccyx, but are continuous with those of the opposite side behind the anal canal. The upper edge of the muscle is ill-defined, since fibers are given off from it to join the levator ani. The action of this muscle is peculiar. From Wikipedia, the free encyclopedia. Sphincter ani externus muscle Coronal section through the anal canal.
Overview of the Anal Sphincter
Sign up. Illustrated anatomical parts with images from e-Anatomy and descriptions of anatomical structures. Description: The Sphincter ani externus External sphincter ani is a flat plane of muscular fibers, elliptical in shape and intimately adherent to the integument surrounding the margin of the anus.
An anal sphincter is a group of muscles at the end of the rectum that surrounds the anus and controls the release of stool, thereby maintaining continence. There are two sphincter muscles: one is internal and one is external. The external anal sphincter muscle helps maintain continence and keep stool in the rectum.