[Functional anatomy of the pelvic floor]

Abstract

The pelvic floor is the support of the pelvic visceras. The levator ani muscle (LA) with its two bundles (pubo- and ilio-coccygeus) is the major component of this pelvic floor. LA is formed essentially by type I fibers (with high oxidative capability and presence of slow myosin) as in postural muscles. The aerobic metabolism makes LA susceptible to injury caused by excentric contraction and mitochondrial dysfunction. The innervation of the pelvic floor comes from the 2nd, 3rd, 4th anterior sacral roots; denervation affects pelvic dynamism. Perineum includes the musculofascial structures under the LA: ventrally the striated urethral sphincter and the ischio-cavernous and bulbospongious, caudally the fatty tissue filling the ischioanal fossa. Pelvic fascia covers the muscles; it presents reinforcements: the uterosacral and cardinal ligaments, the arcus tendineus fascia pelvis (ATFP) and the arcus tendineus levator ani (ATLA). The pelvis statics is supported by the combined action of all this anatomical structures anteriorly forming the perineal "hammock", medially the uterosacral and cardinal ligaments, posteriorly the rectovaginal fascia and the perineal body. The angles formed by the pelvic visceras with their evacuation ducts participate to the pelvic statics. During the pelvic dynamics the modification of these angles expresses the action of the musculofascial structures.