COMMOX ILIAC 565 



It \\ ill be thus seen that the right common iliac artery crosses both common 

 iliac veins, and that its own vein, the right, is at first a little to the left side, l)ut, 

 as it ascends, i»asses beneath it, and gets a little to the right side. Since the bifur- 

 cation of the vena cava is a little lx4o\v and to the right side of the l)ifurcation of 

 the aorta, it follows that the right common iliac artery lies on the conmiencement 

 of the vena cava. 



The Left Coimmon Iliac Artery 



The left common iliac artery, one inch and three-quarters in length (4 cm.), 

 is a little shorter and thicker than the right. 



Relations. — In front it is covered by the peritoneum, which separates it from 

 the intestines, and is crossed by the ureter, the ovarian artery in the female, 

 branches of the sympathetic nerve descending to the hypogastric plexus, the termi- 

 nation of the inferior mesenteric artery, the sigmoid flexure, and the sigmoid 

 meso-colon. 



Behind are the lower border of the body of the fourth lumbar vertebra, the disc 

 betwcL-n the fourth and fifth lumbar vertebrae, the body of the fifth lumbar 

 vertebra, and the disc between it and the sacrum. Crossing deeply behind the 

 artery between the fifth lumbar vertebra and the psoas, is the obturator nerve, the 

 luml)0-sacral cord, and the ilio-lumbar artery. 



To the left side is the psoas muscle. 



To tlie right side are the left common iliac vein, the hypogastric plexus, and 

 the middle sacral arterv. 



Variations in the Common Iliac Arteries 



(A) The cotumon iliac arteries may be longer or shorter than here described. Thej- liave 

 been found as short as half an inch, or as long as four and a half inches, but the usual limit is 

 something between one and a half to three inches. This variation in the length of the vessels 

 may depend upon the aorta bifurcating above or below tlie usual spot, or upon the common iliac 

 arteries dividing higher or lower than usual. A low bifurcation of the aorta is somewhat more 

 comuion than a high bifurcation, as is also the case with the common iliacs. (B) The common 

 iliacs may be absent, the external and internal iliacs then arising together from the end of the 

 aorta. (C) Either artery may give off a large branch, such as tlie ilio-lumbar, the lateral or the 

 middle sacral, .sometimes a lumbar, or occasionally an accessory renal arterj'. 



Collateral Circulation 



The collateral circulation after obstruction or ligature of the common iliac artery is carried 

 on chiefly (fig. 374) by the anastomosis of the middle sacral with the lateral sacral; the internal 

 mammary with the epigastric ; the lumbar arteries of the aorta with the ilio-lumbar and deep 

 circumflex iliac ; the pubic branch of the epigastric with the jaibic branch of tlie obturator ; 

 the posterior branches of the sacral arteries with the gluteal ; the superior hajmorrhoidal from 

 the superior mesenteric, with the hjemorrhoidal branches of the internal iliac and jmdic ; the 

 ovarian arteries from the aorta with the uterine branches of the internal iliac ; and by the 

 anastomosis across the middle line of the jmbic branch of the obturator with the like vessel of 

 the opjwsite side ; the lateral sacral with the opposite lateral sacral ; and the vesical, hsemor- 

 rhoidal, uterine, and vaginal branches of the internal iliac with the corresponding branches of 

 the opposite internal iliac. 



Branches of the Common Iliac Artery 



The branches of the common iliac artery are: — (1) Peritoneal and sub- 

 peritoneal; (2) ureteral: ^-'5) iiitti-n;il iliac; and (4) external iliac. 



(1) The peritoneal and subperitoneal are distriiiuted to the peritoneum and 

 subperitoneal fat. They anastomose with like vessels given off from the lumbar, 

 phrenic, and renal arteries, forming a suljperitoneal arterial anastomosis. They 

 are very small and unimportant. 



(2) The ureteral are .small insignificant twigs given off to the ureter as that 

 duct crosses the artery. They anastomose with the ureteral arteries given off from 

 the si3ermatic above, and with those derivcil from the vesical arteries below. 



