anorectalis

Anorectalis is not a standard term in modern human anatomy and may appear in older or non-primary texts. In contemporary references, the muscles of the anorectal region are usually described as part of the levator ani, with the puborectalis muscle singled out as a key component. Some sources historically used anorectalis to refer to the muscular structures surrounding the anorectal junction, but this usage is not widely maintained in current nomenclature.

Anatomy and relationships: The puborectalis muscle originates from the posterior surface of the pubic bone and loops behind the anorectal junction to insert on the opposite side, forming a sling around the rectum. This sling, together with the rest of the levator ani, supports the pelvic floor. The puborectalis forms a major part of the mechanism that maintains the anorectal angle, which helps keep the rectum closed at rest. The external anal sphincter and internal anal sphincter are distinct sphincteric structures located near the anal canal, and they interact with the puborectalis in maintaining continence.

Function: The primary role attributed to the puborectalis and adjacent muscles is to maintain continence by sustaining an acute anorectal angle at rest. During defecation, voluntary relaxation of the pelvic floor muscles, including the puborectalis, allows the angle to straighten and the rectum to align with the anal canal, in coordination with the sphincters and pelvic floor dynamics.

Clinical relevance: Weakness or injury to the pelvic floor muscles, including components of the levator ani, can contribute to fecal incontinence, pelvic organ prolapse, or defecatory disorders. Evaluation may involve physical examination and imaging such as MRI or ultrasound, with treatment ranging from pelvic floor rehabilitation to surgical options in selected cases.