Levator Ani Muscle Anatomy

The levator ani is a tripartite, funnel-shaped muscular sheet formed by the puborectalis, pubococcygeus, and iliococcygeus muscles. In addition to the levator’s general role of supporting abdominopelvic viscera as part of the pelvic diaphragm, the puborectalis is particularly involved in maintaining fecal continence.

It is the larger and more important part of the pelvic floor that is formed by the bowl – or funnel – shaped pelvic diaphragm, which consists of the coccygeus and levator ani muscles and the fascias (L. fasciae) covering the superior and inferior aspects of these muscles. The pelvic diaphragm lies within the lesser pelvis, separating the pelvic cavity from the perineum, for which it forms the roof.

The levator ani is attached to the bodies of the pubic bones anteriorly, the ischial spines posteriorly, and a thickening in the obturator fascia (the tendinous arch of the levator ani) between the two bony sites on each side.

See Also: Hip Muscles Anatomy

Levator Ani Muscle Anatomy

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 coccyx (often referred to clinically as the “levator plate”). Shorter muscular slips of pubococcygeus extend medially and blend with the fascia around midline structures and 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 (e.g., the intestines). 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 (e.g., 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 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.

The perineum, levator ani, and ligaments of the pelvic fascia may be injured during childbirth. The pubococcygeus and puborectalis, the main and most medial parts of the levator ani, are the muscles torn most often. These parts of the muscle are important because they encircle and support the urethra, vagina, and anal canal. Weakening of the levator ani and pelvic fascia (e.g., tearing of the paracolpium), from stretching or tearing during childbirth, may decrease support for the vagina, bladder, uterus, or rectum or alter the position of the neck of the bladder and the urethra.

Origin	Puborectalis: Posterior surface of bodies of pubic bones (also known as puboanalis) Pubococcygeus: Posterior surface of bodies of pubic bones (lateral to puborectalis) Iliococcygeus: Tendinous arch of interal obturator fascia, Ischial spine
Insertion	Puborectalis: None (forms ‘puborectal sling’ posterior to rectum) Pubococcygeus: Anococcygeal ligament, Coccyx, Perineal body and musculature of prostate/ vagina Iliococcygeus: Anococcygeal ligament, Coccyx
Innervation	Nerve to levator ani (S4); Pubococcygeus also receives branches via inferior rectal/ perineal branches of Pudendal nerve (S2- S4)
Blood Supply	Inferior gluteal, inferior vesical and pudendal arteries
Action	Stability and support of the abdominal and pelvic organs, resistance against increased intra-abdominal pressure, opening and closing of the levator hiatus

References & More

1. Clinically Oriented Anatomy – 8th Edition
2. Gowda SN, Bordoni B. Anatomy, Abdomen and Pelvis: Levator Ani Muscle. [Updated 2022 Oct 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed