THE INTERNAL ILIAC ARTERY 677 



Relations. Within the pelvis, it lies in front of the Pyriformis muscle and sacral plexus of 

 nerves, and the sciatic artery, and on the outer side of the rectum (on the left side). As it 

 crosses the spine of the ischium it is covered by the Gluteus maxim us and overlapped by the great 

 sacrosciatic ligament. Here the pudic nerve lies to the inner side and the nerve to the Obturator 

 internus to the outer side of the vessel. In the pelvis it lies on the outer side of the ischiorectal 

 fossa, upon the surface of the Obturator internus muscle, contained in a fibrous canal (Alcock's 

 canal), formed by the splitting of the obturator fascia. It is accompanied by the pudic veins 

 and the pudic nerve. 



Peculiarities. The internal pudic is sometimes smaller than usual, or fails to give off one 

 or two of its usual branches; in such cases the deficiency is supplied by branches derived from 

 an additional vessel, the accessory pudic, which generally arises from the internal pudic artery 

 before its exit from the great sacrosciatic foramen. It passes forward along the lower part of 

 the bladder and across the side of the prostate gland to the root of the penis, where it perforates 

 the triangular ligament and gives off the branches usually derived from the pudic artery. The 

 deficiency most frequently met with is that in which the internal pudic ends as the artery of the 

 bulb, the artery of the corpus cavernosum and dorsal artery of the penis being derived from the 

 accessory pudic. Or the pudic may terminate as the superficial perineal, the artery of the bulb 

 being derived, with the other two branches, from the accessory vessel. Occasionally the acces- 

 sory pudic artery is derived from one of the other branches of the internal iliac, most frequently 

 the inferior vesical or the obturator. 



Branches. The branches of the internal pudic artery are: 



Muscular. Artery of the bulb. 



Inferior hemorrhoidal. Urethral artery. 



Superficial perineal. Artery of the corpus cavernosum. 



Transverse perineal. Dorsal artery of the penis. 



The muscular branches consist of two sets one given off in the pelvis, the 

 other as the vessel crosses the ischial spine. The former are several small offshoots 

 which supply the Leva tor ani, the Obturator internus, the Pyriformis, and the 

 Coccygeus muscles. The branches given off outside the pelvis are distributed to 

 the adjacent part of the Gluteus maximus and External rotator muscles. They 

 anastomose with branches of the sciatic artery. 



The inferior hemorrhoidal artery (a. haemorrhoidalis inferior) arises from 

 the internal pudic as it passes above the tubercsity of the ischium. Crossing 

 the ischiorectal fossa it is distributed by two or three terminal branches to the 

 muscles and integument of the anal region. Instead of one inferior hemor- 

 rhoidal artery two or three small vessels may arise from the internal pudic. 



The superficial perineal artery (a. perinei) (Fig. 476) supplies the scrotum and the 

 muscles and integument of the perineum. It arises from the internal pudic in 

 front of the preceding branches, and turns upward, crossing either over or under 

 the Transversus perinei superficialis muscle, and runs forward, parallel to the 

 pubic arch, in the interspace between the Accelerator urinae (ra. bulbocavernosus) 

 and Erector penis (m. ischiocavernosus) muscles, both of which it supplies, and is 

 finally distributed to the skin and dartos of the scrotum. In its passage through 

 the perineum it lies beneath the superficial perineal fascia. 



The transverse perineal artery is a small branch which arises either from the 

 internal pudic or from the superficial perineal artery as it crosses the Transversus 

 perinei muscle. It runs transversely inward along the cutaneous surface of the 

 Transversus perinei superficialis muscle and anastomoses with the like vessel 

 of the opposite side, and with the superficial perineal and inferior hemorrhoidal 

 arteries. It supplies the Transversus perinei and the structures between the 

 anus and bulb of the urethra. 



The artery of the bulb (a. bulbi urethrae) is a short vessel of large caliber which 

 ar/.sr.v from the internal pudic between the two layers of the triangular ligament: 

 it passes nearly transversely inward, through the fibres of the Compressor urethrae 

 muscle, pierces the superficial layer of the triangular ligament, and gives off 



