The levator ani consists of three parts, often poorly demarcated but designated according to attachments and fiber course:

• Puborectalis: the thicker, narrower, medial part of the levator ani, consisting of muscle fibers that are continuous between the posterior aspects of the bodies of the right and left pubic bones. It forms a U-shaped muscular sling (puborectal sling) that passes posterior to the anorectal junction, bounding the urogenital hiatus. This part plays a major role in maintaining fecal continence.

• Pubococcygeus: the wider but thinner intermediate part of the levator ani, which arises lateral to the puborectalis from the posterior aspect of the body of the pubis and anterior tendinous arch. It passes posteriorly in a nearly horizontal plane; its lateral fibers attach to the coccyx and its medial fibers merge with those of the contralateral muscle to form a fibrous raphe or tendinous plate, part of the anococcygeal body or ligament between the anus and the coccyx (often referred to clinically as the “levator plate”).

Shorter muscular slips of the pubococcygeus extending medially and blending with the fascia around midline structures are named for the structure near their termination: pubovaginalis (females), puboprostaticus (males), puboperinealis, and pubo-analis.

• Iliococcygeus: the posterolateral part of the levator ani, which arises from the posterior tendinous arch and ischial spine. It is thin and often poorly developed (appearing more aponeurotic than muscular), and also blends with the anococcygeal body posteriorly.

The levator ani forms a dynamic floor for supporting the abdominopelvic viscera. It is tonically contracted most of the time to support the abdominopelvic viscera, and to assist in maintaining urinary and fecal continence. It is actively contracted during activities such as forced expiration, coughing, sneezing, vomiting, and fixation of the trunk during strong movements of the upper limbs (e.g., when lifting heavy objects), primarily to increase support of the viscera during periods of increased intra-abdominal pressure, and perhaps secondarily to contribute to the increased pressure (to aid expulsion).

Penetrated centrally by the anal canal, the levator ani is funnel shaped, with the U-shaped puborectalis looping around the “funnel spout”; its tonic contraction bends the anorectum anteriorly. Active contraction of the (voluntary) puborectalis portion is important in maintaining fecal continence immediately after rectal filling or during peristalsis when the rectum is full and the involuntary sphincter muscle is inhibited (relaxed).

The levator ani must relax to allow urination and defecation. The increased intra-abdominal pressure for defecation is provided by contraction of the (thoracic) diaphragm and muscles of the anterolateral abdominal wall. Acting together, the parts of the levator ani elevate the pelvic floor after their relaxation and the consequent descent of the pelvic diaphragm that occurs during urination and defecation.