574 



THE ARTERIES 



(3) In the third part of its course, as it lies on the obturator internus muscle, 

 in the outer wall of the ischio-rectal fossa, it is placed about an inch and a half 

 (3"5cm. ) above the lower margin of the tuberosity of the ischium. It is here 

 bound down to the muscle by a strong sheath of the obturator layer of the pelvic 

 fascia (Alcock's canal). In this part of its course the dorsal nerve of the penis 

 and the superficial perineal nerve, into which the pudic nerve divides about tliis 

 situation, lie respectively above and l)elow the artery. 



The branches of the pudic artery in the third part of its course are: — (a) The 

 external or inferior hajmorrhoidal; and (h) the superficial j^erinseal. 



(a) The external or inferior haemorrhoidal branches (inferior or posterior 

 anal) are given off from the pudic at the posterior jiart of the ischio-rectal fossa, 

 just after it enters the outer wall of that cavity through the lesser sciatic foramen. 

 They perforate the sheath of obturator fascia binding the pudic artery to the 



Fig. 370a. — The Arteries of the Perineum. 



On the right side Colles's fascia has been turned back to show the superficial vessels. On the 

 left side the superficial vessels have been cut away with the anterior layer of the triangular ligament 

 to show the deep vessels. 



Superficial perinaeal vessels 



Accelerator uriuae 



Colles's fascia, turned back 



Erector penis 



Transverse peri)iiml vessels 



Cut edge of triangular 



ligament 



SUPERFICIAL PERIX^AL 



NER VE GIVING OFF 



TRANSVERSE BRANCH 



Pudic vessels 



Inferior hcemorrhoidal vessels 

 and nerves 



Gluteus raaximus, 

 hooked back 



Crus penis 



Dorsal artery of penis 

 Artery of cms 



■A — Artery of bulb 



COWPER'S 6LAN0 



.. ,j- — . Pudic artery 



\\ 

 =y-],i Great sciatic ligament 



*—ji Levator ani 



External sphincter 



Gluteus maximus 



obturator internus, and course transversely through the fat of the ischio-rectal 

 fossa, inwards to the anus, where they supply the sphincter muscle and levatc^r ani, 

 and anastomose with the superior and middle ha?morrhoidal arteries. Twigs are 

 given off from them to the skin covering the anal triangle of the ])erina3um; otlier 

 branches supply the gluteus maximus and wind over the posterior fold of tliat 

 muscle to the integuments; whilst others again run forwards and anastomose with 

 the transverse and sujierficial perinatal arteries (fig. 370a). 



(h) Th(! superficial perinaeal branch arises from the pudic at the front of the 

 ischio-rectal fossa, just l)ef ore that vessel ])ierces the posterior layer of the triangular 

 ligament. It passes through the deep layer of the superficial fascia of the peri- 

 naeum (Colles's fascia), Avhere that structure is continued into the anterior layer of 

 the triangular ligament round the transverse perinatal muscle. It then crosses in 

 front of (occasionally l^'hind) that muscle, and enters the periiia'al triangle, the 



