494 



THE MUSCULAE SYSTEM. 



the origin of the anal canal, (3) the ano-coccygeal raphe behind the anus, and (4) 

 into the sides of the lower coccygeal vertebrae. 



The levator ani muscle fills up and completes the pelvic floor on each side of 

 the median plane. Enclosed in a sheath derived from the general pelvic fascia 

 along the arcus tendineus, the muscle presents an upper concave surface in 

 relation to the pelvic cavity, prostate gland (or vagina), and rectum, and an 



Sacro-tuberous 

 ligament (cut) 



Extra- 

 peritoneal 

 tissue 



Spina ischia 

 dica (cut) 



ISCHIO- 

 CAVERNOSUS 



Transversus perinei 

 superh'cialis 

 Superior fascia of the 

 urogenital diaphragm 

 SPHINCTER URETHRA 

 MEMBRANACE.E 

 Inferior fascia of the urogenital 

 diaphragm 



The arcus 



tendineus of the 



pelvic fascia 



Pubic bone 

 (cut) 



SPHINCTER ANI 

 EXTERNUS 



FIG. 437. THE FASCIAL AND MUSCULAR WALL OF THE PELVIS AFTER REMOVAL OF PART OF THE 



LEFT HIP BONE. 



inferior convex surface which appears in the perineum and forms the medial wal 

 of the ischio-rectal fossa. 



The levator ani is divisible into four parts puborectalis, pubococcygeus, ilk 

 coccygeus, and iliosacralis. The puborectalis (levator prostatae) is the part inserted int 

 the central point of the perineum. The pubococcygeus is the part inserted into the ami 

 and the ano-coccygeal raphe, and the iliococcygeus and ischiococcygeus are represents 

 by the fibres attached to the sacrum and coccyx. The first two are best developed ; th 

 last two series of fibres are the most rudimentary. These several parts of the muscl 

 represent the remains of the flexor caudae of tailed animals. 



Nerve-Supply. The levator ani is supplied from two sources : by the perineal (muscula 

 branch of the pudendal nerve, and, on its pelvic surface, by special branches from the thil 

 and fourth sacral nerves. 



