ARTERIES 85 



i inches above bifurcation. Lies at first on left side 

 of aorta, then crosses over left psoas, left common iliac and 

 ureter, to back of rectum ; supplies descending, iliac and 

 pelvic parts of colon and rectum. 



Branches : 



Left colic : directed upwards in front of left kidney, ascending 

 branch anas, middle colic; descending branch supplies descend- 

 ing colon ; anas, sigmoid and superior haemorrhoidal. 



Sigmoid : to iliac and pelvic colon ; anas, left colic and 

 superior haemorrhoidal. 



Superior h&morrhoidal : continuation of inferior mesenteric 

 trunk, passes behind rectum and divides in meso-rectum into 

 two branches, which pass down, one on either side, to about 

 6 inches from anus, where they subdivide to supply pelvic 

 colon and rectum ; anas, sigmoid, middle and inferior 

 haemorrhoidals. 



Lumbar (5 pairs] : arise from back of aorta, pass outwards, 

 resting on body of corresponding vertebrA underneath sym- 

 pathetic and psoas ; the two upper pairs under crura of 

 diaphragm ; the right ones also under vena cava. Divide 

 near transverse processes into : 



Abdominal : coursing outwards beneath quadratus (the first 

 pair cross quadratus), to end between muscles of abdominal 

 wall ; anas, deep epigastric, internal mammary, intercostals, 

 ilio-lumbar, circumflex iliac. 



Dorsal : accompanies posterior primary branch of nerve, 

 gives off spinal branch to supply meninges and cord ; anas. 

 intercostal. 



Middle sacral : a small branch given off just at bifurcation 

 courses over 5th lumbar vertebra and middle of sacrum to 

 coccyx behind the left common iliac vein, anas, lateral sacral. 



THE COMMON ILIAC ARTERY. 



Extent. From bifurcation of aorta, on body of 4th lumbar 

 vertebra, to opposite lumbo-sacral articulation, there dividing 

 into external and internal iliac. About 2 inches long. 



Relations. In front. Peritoneum, small intestines, ureter, 

 branches of sympathetic. 



Differences between right and left artery. The right one is the 

 longer, the aorta being on the left side of spine ; on right 

 side are inferior vena cava and right psoas. Companion vein 

 at first behind, but to the right at upper part ; left common 

 iliac vein behind. The left one is crossed anteriorly by 

 inferior mesenteric artery, the companion vein being below 

 and internal. 



