PELVIC FASCLE AXD MUSCLES 



1061 



The obturator fascia (figs. 648, 650) is attached abore to the iHo-j»uhic line, 

 as far back as the sacio-ihac joint and to the posterior lij) of the crest; helov:, to 

 the l)ack of the symphysis, the inner lip of the lower border of the isclno-i)ul>ic 

 ramus, and the inner l>order of the ischial tuberosity; and behind it skirts tlie 

 osseous border of the great sciatic notch as far as tlie ischial spine, but at the lesser 

 sciatic notch passes out of the i>elvis with the muscle, and ajtpears in the post- 

 femoral region of the thigh. At its Ijorders it is closely related to the fascia iliaca 

 above, the fascia of the pyriformis behind, and the dee}) triangular ligament below. 

 Its outer surface is in contact with the muscular fibres of the obturator intemus; its 

 inner surfare is divided into tAvo portions by a curved l)and of fibres called the 

 ' white line ' or arcus tendineus, extending from the inner aspect of the ischial 

 si)ine to tin- back of the os i)ul»is, a little external to the symphysis. The upper 

 or pelvic segment above the white line is separated from the pelvic viscera by 

 sul>peritoneal tissue; the lower or ischio-rectal segment, Ijelow the line, enters 

 into the formation of the outer wall of the ischio-rectal fossa. This portion forms 

 a sheath (canal of Alcock) for the pudic vessels and nerves about an incli above 

 the inner margin of the tuber ischii. The fascia gives oft" from its inner surface at 



Fig. 649.— Muscles of the Floor of the Pelvis. 



PyriformiB 



Levator ani 'divided 

 below the " white line ' i 



Space for obturator 

 intemus 



!'<i.isnge for gluteal 

 vessels and nerve 



Pyriformis 

 Passage for sciatic 



II nd pudic vessels 



and nerve 



SCHIAL SPINE 



;;occygeu8 

 Callular interval 

 Levator ani 



Capsule of prostate, 

 and pubo-prostatic 

 ligaments 



the white line two thin laminte: one, the recto-vesical, to the visceral surface of the 

 levator ani; the other, the ischio-rectal, to the parietal aspect of the same nmscle. 



The levator ani muscle (figs. 648, 650), with its fellow of the opposite side, 

 constitutes the greater part of the muscular floor of the pelvis, and acts as a septum 

 between the pelvic cavity and the ischio-rectal fossa. It arises anteriorly from the 

 back of the os pubis, just external to the attachment of the pubo-vesical musrle, 

 posteriorly from the inner side of the ischial spine below the origin of the coccyg- 

 eus, and between these two points from the whole length of the "white line.' Its 

 fibres form a Hat plane of consideraV>le strength, and pass downwards, backwards, 

 and inwards to their insertion, the most posterior into the tip of the coccyx; those 

 next in order joining the opposite muscle in a nu-dian raphe extending from tlie 

 coccyx to the tendinous centre of the perinanmi. and the rest becoming lost ujton the 

 side of the rectum, interlacing with the longitudinal layer of the muscular wall of the 

 gut, a few fil)res perhajis running in front to the preanal raphe. Its two surfaces may 

 be termed visceral and ])arietal; the former, looking forwards as well as upwards, is 

 invested by a layer of fascia, the recto-vesical, and is further separated from the 

 lower part of the bladder by suliperitoneal tissue; the parietal surface, covered by 

 a fascia, the ischio-rectal or anal, forms the greater })art of the outer wall of the 

 ischio-rectal fos^a. The anterior and posterior l)orders of the muscle are free (and 



