#16 COMMON ILIAC ARTERIES. 



artery runs along the lower border of the last rib, and the last along the 

 crest of the ilium. In passing between the psoas muscles and the verte- 

 brae, they are protected by a series of tendinous arches, which defend 

 them and the communicating branches of the sympathetic nerve from 

 pressure during the action of the muscle. 



The SACRA MEDIA arises from the posterior part of the aorta at its bifur- 

 cation, and descends along the middle of the anterior surface of the sacrum 

 to the first piece of the coccyx, where it terminates by inosculating with 

 the lateral sacral arteries. It distributes branches to the rectum and ante- 

 rior sacral nerves, and inosculates on either side with the lateral sacral 

 arteries. 



Varieties in the Branches of the Abdominal Jlorta. The phrenic arteries 

 are very rarely both derived from the aorta. One or both may be branches 

 of the cceliac axis ; one may proceed from the gastric artery, from the 

 renal, or from the upper lumbar artery. There are occasionally three or 

 more phrenic arteries. The cceliac artery is very variable in length, and 

 gives off its branches irregularly. There are sometimes two or even three 

 hepatic arteries, one of which may be derived from the gastric or even 

 from the superior mesenteric. The colica media is sometimes derived 

 from the hepatic artery. The spermatic arteries are very variable, both in 

 origin and number. The right spermatic may be a branch of the renal 

 artery, and the left a branch of the inferior mesenteric. The supra-renal 

 arteries may be derived from the phrenic or renal arteries. The renal 

 arteries present several varieties in number ; there may be three or even 

 four arteries on one side, and one only on the other. When there are 

 several renal arteries on one side, one may arise from the common iliac 

 artery, from the front of the aorta near its lower part, or from the internal 

 iliac. 



COMMON ILIAC ARTERIES. 



The abdominal aorta divides opposite the fourth lumbar vertebra into 

 the two common iliac arteries. Sometimes the bifurcation takes place as 

 high as the third, and occasionally as low as the fifth lumbar vertebra. 

 The common iliac arteries are about two inches and a half in length ; they 

 diverge from the termination of the aorta, and pass downwards and out- 

 wards on each side to the margin of the pelvis, opposite the sacro-iliac 

 symphysis, where they divide into the internal and external iliac arteries. 

 In old persons the common iliac arteries are more or less dilated and 

 curved in their course. 



The Right common iliac is somewhat longer than the left, and forms a 

 more obtuse angle with the termination of the aorta ; the angle of bifur- 

 cation is greater in the female than in the male. 



Relations. The relations of the two arteries are different on the two 

 sides of the body. The right common iliac is in relation in front with the 

 peritoneum, and is crossed at its bifurcation by the ureter. It is in rela- 

 tion posteriorly with the two common iliac veins, and externally with the 

 psoas magnus. The left is in relation in front with the peritoneum, and 

 is crossed by the rectum and superior hasmorrhoidal artery, and, at its 

 bifurcation, by the ureter. It is in relation behind with the left common 

 iliac vein, and externally with the psoas magnus. 



