Pelvic diaphragm

The pelvic diaphragm (pelvic floor) is composed of muscle fibers of the levator ani, the coccygeus muscle, with which may be included the parietal pelvic fascia on their upper and lower aspects. The pelvic diaphrgam separates the pelvic cavity above from the perineal region (including perineum) below.

The right and left levator ani lie almost horizontally in the floor of the pelvis, separated by a narrow gap that transmits the urethra, vagina, and anal canal. The pubococcygeus, the main part of the levator, runs backward from the body of the pubis toward the coccyx and may be damaged during birth. Some fibers are inserted into the prostate, urethra, and vagina. The right and left puborectalis unite behind the anorectal junction to form a muscular sling. Some regard them as a part of the external anal sphincter. The iliococcygeus, the most posterior part of the levator ani, is often poorly developed.

The coccygeus, situated behind the levator ani and frequently tendinous as much as muscular, extends from the ischial spine to the lateral margin of the sacrum and coccyx.

The pelvic cavity of the true pelvis has the pelvic floor as its inferior border (and the pelvic brim as its superior border). The perineum has the pelvic floor as its superior border.