i6 2 ABDOMEN 



UROGENITAL TRIANGLE. 



The superficial fascia of the urogenital triangle has already 

 been studied (p. 151). The following structures which lie in 

 the area still require to be dissected : 



1. The posterior scrotal vessels and nerves. 



2. The long perineal branch of the posterior cutaneous nerve of the thigh. 



3. The root of the penis. {The bulb of the urethra and the crura. 



fa. Superficial transverse perineal 



4. The superficial perineal muscles. L Bul ^emosus muscle. 



(/. Ischio-cavernosus muscle. 



5. Inferior fascia of the urogenital diaphragm. 



6. The internal pudendal vessels and their branches and the pudendal 



nerve and its branches. 



7. The deep transverse perineal muscle and the sphincter of the mem- 



branous urethra. 



8. "The bulbo-urethral glands. 



9. The membranous portion of the urethra. 

 10. Superior fascia of the urogenital diaphragm. 



Dissection. Clear away the remains of the fascia of Colles 

 from the urogenital triangle ; then clean the perineal artery and 

 follow its terminal scrotal branches to the scrotum. Clean 

 also the posterior scrotal branches of the superficial division of 

 the perineal nerve, and whilst cleaning them find the long 

 perineal branch of the posterior cutaneous nerve of the thigh. 

 It communicates with the posterior scrotal nerves in the perineal 

 pouch. When it is found, trace its terminal branches to the 

 scrotum, and trace its trunk backwards to the point where it 

 enters the superficial pouch of the perineum by piercing the fascia 

 of Colles, about 25 mm. (one inch) anterior to the tuberosity 

 of the ischium. As the nerves are followed three muscles will 

 be more or less displayed : Along the margin of the pubic arch 

 the ischio-cavernosus ; near the median plane the bulbo- 

 cavernosus; and, crossing between their posterior extremities, 

 the superficial transverse perineal muscle. 



Superficial Arteries and Nerves. 



I- The perineal artery. 



2. The transverse branch of the perineal artery. 



The posterior scrotal nerves. 



Nerves. - 2. The long perineal branch of the posterior cutaneous nerve 

 of the thigh. 



2. 

 ( i. 

 -| 2. 

 ( 



The perineal artery, a branch of the pudendal, .pierces first 

 the medial wall of the canal in the obturator fascia, then the 

 base of Colles' fascia, and so it gains the interior of the 

 perineal pouch of fascia. In the pouch it crosses superficial 

 to the transversus perinei muscle, and is continued forwards, 

 in the interval between the bulbo-cavernosus and ischio- 



