The levator ani muscle is a broad, funnel-shaped muscle composed of striated fibers, forming a key part of the pelvic floor. It plays an important role in various bodily functions and contributes to pelvic health and stability.
Precise Anatomical Position
The levator ani muscle is located in the lower part of the pelvis, forming a broad muscular sheet that creates a substantial portion of the pelvic floor. It originates from the posterior surface of the pubic bone anteriorly, the inner surface of the ischial spines posteriorly, and the obturator fascia, a fibrous sheet covering the obturator internus muscle.
From these origins, the muscle fibers extend towards the center of the pelvis, meeting in the midline and inserting into the coccyx and a fibrous band known as the anococcygeal raphe. This arrangement creates a sling-like structure that supports the pelvic organs from below. The levator ani forms a V-shaped structure, with its two “arms” defining a central opening called the levator hiatus. This opening allows for the passage of structures such as the urethra and rectum, and in females, the vagina.
Constituent Muscles of the Levator Ani
The levator ani is not a single muscle but rather a complex group comprised of three distinct muscles: the puborectalis, pubococcygeus, and iliococcygeus.
The puborectalis muscle is the most medial and the thickest part of the levator ani. It originates from the lower part of the pubic bone and forms a U-shaped sling that wraps around the rectum. This muscle forms a continuous loop by meeting fibers from the opposite side, creating a bend in the anorectal junction.
Adjacent to the puborectalis is the pubococcygeus muscle, which originates from the posterior aspect of the pubic bone and the anterior part of the obturator fascia. Its fibers extend backward, inserting into the anococcygeal raphe and the coccyx.
The iliococcygeus muscle forms the posterolateral portion of the levator ani. It originates from the inner surface of the ischial spine and the tendinous arch of the obturator fascia. This muscle then extends posteriorly, inserting into the coccyx and the anococcygeal raphe, where its fibers merge with those from the opposite side.
Its Role Based on Location
The levator ani muscle’s placement within the pelvis directly enables its many functions. Its broad, sling-like configuration across the pelvic outlet allows it to serve as a supportive floor for the pelvic organs. This includes providing structural support to the bladder, uterus (in females), and rectum, helping to maintain their proper positions.
The levator ani also plays an important role in maintaining continence. The puborectalis muscle, by forming a sling around the rectum and creating an angle at the anorectal junction, assists in preventing involuntary bowel movements. The overall muscle group helps regulate the urethral and anal sphincters, contributing to both urinary and fecal control. The muscle’s tonic activity stabilizes these organs and helps control the opening and closing of the levator hiatus.