568 



THE BLOOD-VASCULAR SYSTEM. 



muscle, and escapes from the pelvis through this foramen between the Pyriformis 

 and Coccygeus. It then descends in the interval between the trochanter major and 



tuberosity of the ischium, ac- 

 companied by the sciatic nerves, 

 and covered by the Gluteus 

 maximus, and is continued down 

 the back of the thigh supplying 

 the skin, and anastomosing with 

 branches of the perforating arte- 

 ries. 



Within the, pelvis it distrib- 

 utes branches to the Pyriformis, 

 Coccygeus, and Levator ani 

 muscles ; some hsemorrhoidal 

 branches, which supply the 

 rectum, and occasionally take 

 the place of the middle haemor- 

 rhoidal artery; and vesical 

 branches to the base and neck 

 of the bladder, vesiculge semi- 

 nales, and prostate gland. Ex- 

 ternal to the pelvis it gives off 

 the following branches : 

 Coccygeal. 

 Inferior Gluteal. 

 Comes Nervi Ischiadici. 

 Muscular. 

 Anastomotic. 

 Articular. 



The coccygeal branch runs 

 inward, pierces the great sacro- 

 sciatic ligament, and supplies 

 the Gluteus maximus, the in- 

 tegument, and other structures 

 on the back of the coccyx. 



The inferior gluteal branches, 

 three or four in number, supply 

 the Gluteus maximus muscle, 

 anastomosing Avith the gluteal 

 artery in the substance of the 

 muscle. 



The comes nervi ischiadici 

 is a long, slender vessel which 

 accompanies the great sciatic 

 nerve for a short distance ; it 

 then penetrates it and runs in 

 its substance to the lower part 

 of the thigh. 



The muscular branches supply the Gluteus maximus, anastomosing with the 

 gluteal artery in the substance of the muscle : the external rotators, anastomosing 

 with the internal pudic artery ; and the muscles attached to the tuberosity of the 

 ischium, anastomosing with the external branch of the obturator and the internal 

 circumflex arteries. 



The anastomotic artery is directed downward across the external rotators, and 

 assists in forming the so-called crucial anastomosis by anastomosing with the 

 superior perforating and the internal and external circumflex. 



Termination 

 of internal 

 circumflex. 



Superior 

 perforating. 



Middle 

 perforating. 



Inferior 

 perforating. 



Termination of 

 profunda. 



Superior muscular. 



Superior external 

 articular. 



Inferior muscular. 



FIG. 316. The arteries of the gluteal aud posterior femoral 

 regions. 



Superior internal 

 articular. 



