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A muscle, situate at the lower part of the pelvis. It is broad, flat, quadrilateral, and broader above than below. It represents a kind of membranous partition, which closes the outlet of the pelvis, and the upper concavity of which is opposed to that of the diaphragm. It is attached, above, to the posterior surface of the body of the pubis, to the upper part of the obdurator foramen, and to the spine of the ischium; and is inserted into the coccyx, into an aponeurotic line common to it and its fellow, and into the lateral parts of the rectum. This muscle supports the rectum; raises it, and carries it upwards during the evacuation of the excrement. It can, also, compress the bladder and vesiculae seninales, and thus favour the expulsion of the urine and sperm.

A thin, broad muscle arising from the anterior and lateral portions of the inner surface of the true pelvis, the inferior ramus of the pubes and spine of the ischium and the pelvic fascia, uniting with its fellow of the opposite side, and inserted into the side of the lower portion of the coccyx, the side and lower portion of the rectum, and the fascia covering the prostate gland. Its lowermost fibers blend with those of the opposite side and the external and internal sphincters of the anus and the constrictor urethra forming, with the coccygeus, the floor or diaphragm of the pelvis. [Lat.]