Levator ani muscle
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The levator ani muscle, also known as the muscular pelvic diaphragm, is the musculotendinous sheet that forms the majority of the pelvic floor, supports the pelvic viscera, and aids in urinary and fecal evacuation as well as maintaining continence.
The levator ani has three main components, each of which is paired 1,2,5:
pubococcygeus (pubovisceral) muscle
subparts: puboperineal, pubovaginal, puboanal muscles
The pubococcygeus muscle runs posteriorly from the body of the pubis and anterior part of the tendinous arch (part of the obturator fascia) to fuse in the midline at the perineal body and musculature of the prostate/vagina 7.
The iliococcygeus muscle runs from the posterior part of the tendinous arch to join itself in the midline, forming the anococcygeal raphe which extends from the anal verge to the tip of the coccyx. Anteriorly and medially, it also fuses with the pubococcygeus 7.
Puborectalis takes attachment from the pelvic surfaces of both ischiopubic rami, anterolaterally. It passes posterior to the rectum to form a muscular sling.
The coccygeus muscle (also known as ischiococcygeus) although a muscle of the pelvic floor, is not formally considered part of the levator ani muscle 3. It is a triangular muscle with its base attaching to the lateral aspect of the inferior sacrum and coccyx and apex attached to the ischial spine. It flexes the coccyx anteriorly and partially fuses with the sacrospinous ligament.
The levator ani forms a U-shape and is deficient medially and anteriorly, an area referred to as the urogenital hiatus 6. This region is instead supported by the deep perineal pouch and perineal membrane below 6.
pelvic surface: branches of S3, S4
perineal surface: branches of the pudendal nerve
thinning or aplasia of one or both sides is common (~50%) 4