442 



THE MUSCULATURE 



fossa run the internal pudic vessels and nerves (fig. 401). Above the pelvic 

 diaphragm in the median part of the pelvic cavity are found the bladder, the 

 ampulla of the rectum, and the prostate gland (in the male) or the vagina and 

 uterus (in the female). Laterally on each side there is a subperitoneal space, filled 

 with connective tissue and containing blood-vessels and nerves (fig. 402). Fascise 

 invest each surface of the pelvic diaphragm {diaphragmatic fascia) and extend 

 about the viscera (endopelvic fascia) . 



Fig. 



.397. — Sagittal Section of the Pelvis to Show the Pelvic Diaphragm and External 



Sphincter Ani. 



Urethra 



Vagina 



Sphincter ani externus profundus 

 Sphincter ani externus superficialis 

 Sphincter ani externus subcutaneus 



Arteria sacra 

 media 



Rectum 

 Sphincter ani externus superficialis 



Tendinous aponeu- 

 rosis of pubo- 

 coccygeus 



Raphe formed by 

 ilio-coccygei 

 Sphincter recti 



Sphincter ani ext. profundus 

 Sphincter ani externus subcutaneus 



The muscular apparatus of the anterior or urogenital triangle of the pelvic 

 outlet is much more complicated than that of the posterior or rectal triangle just 

 described. We have seen that between the levator ani muscles of each side in 

 front of tiie rectum there is a slit which extends to the symphysis pubis and that 

 through it, the lower part of the prostate and the urethra extend in the male, the 

 urethra and the vagina in the female. Between the ischio-pubic rami there is 

 .stretched a triangular muscular and fibrous membrane, which likewise surrounds 

 these urogenital ducts and which serves to strengthen the pelvic wall in this 

 region. I'his structure is known as the urogenital trigone (figs. 398, 400, 403). 

 The musculature within it, called by Holl the accessory or urogenital diaphragm, 

 includ(!S two muscles (fig. 398), the sphincter urogenitalis (urethras) and the deep 

 transverse perineal muscle. The sphincter embraces the urc^thra and associated 

 structures. The component fibre-bundles arise chiefly from the fibrous tissue in 

 the angle beneath the symi)hysis pubis, but partly also from the desccmding i:)ubic 

 rami. Th(!y pass analward and me<lialward on each side of the urethra and then 

 partly interdigitate across the median line, partly terminate in a median raphe. 

 Some fibre-bundles embrace in the male the lower part of the prostate and 

 Cowper's gland. In the female the fibr(^-bundles of the sphincter partly terminate 

 in the wall of the vagina. Some of tlieni are continued downward on each side of 

 the vagina and interdigitate; with (ibni-bundles from the deep transverse perineal 

 muscle. The deep transverse perineal muscle (fig. 398) arises on each side from 

 the ischio-pubic ramus. It constitutes a flat band of muscle, the fibre-bundles of 



