354 



The Abdominal Aorta 



of the mesentery, it reaches the right iliac fossa, where it gives a 

 branch to the end of ileum and the beginning of colon, the ileo-colic. 

 The superior mesenteric has a slight convexity to the left, and from 

 this side are given off twelve or fifteen vasa intestini tenuis, which, by 

 dividing and anastomosing, form a series of arches, three or four deep, 

 from which twigs enter the wall of the jejunum and ileum. The 

 highest of the vasa anastomoses with the pancreatico-duodenal loop, 

 the lowest with the ileo-colic. The upper branch of the ileo-colic 

 anastomoses with colica dextra, which comes from the right side of the 

 superior mesenteric to supply the ascending colon. Higher up comes 

 off the colica media, for the transverse colon ; it anastomoses with 

 the colica dextra, and with the colica sinistra on the descending colon. 

 The colica dextra lies behind the peritoneum ; the colica media runs 

 between the two layers of the transverse meso-colon. 



The supra-renals anastomose in the supra-renal capsule with 

 branches of the phrenic and renal arteries. 



The renals arise just below the superior mesenteric, the right being 

 rather longer and higher than the left. Before entering the hilum 

 they give off twigs to the supra-renal capsule and ureter, and to the 

 bed of the kidney. The renal artery lies behind the vein, and in front 

 of the ureter, the right renal passing behind the vena cava. The 

 artery may be given off in several branches, and supplemental renals 

 are sometimes derived from a mesenteric or iliac trunk. 



As the testis or ovary was developed just below the kidney, so the 

 spermatic or ovarian artery arises close below the renal. It is a 

 slender vessel which descends behind the peritoneum obliquely over 

 the psoas and ureter, the right lying also over the vena cava. In the 

 female the artery passes inwards between the layers of the broad 

 ligament to supply the ovary, and it gives off branches to the uterus, 

 Fallopian tube, and round ligament. By the last-named structure 

 some twigs of the ovarian artery may eventually reach the labium. In 

 the male the artery emerges with the other constituents of the sper- 

 matic cord, and may anastomose with the artery of the vas and with 

 the cremasteric branch of the deep epigastric. 



Ths inferior mesenteric is given off within a couple of inches of the 

 bifurcation of the aorta, that is, rather more than an inch above the 

 umbilicus ; it passes over the left common iliac vessels to the upper 

 part of the rectum, down either side of which it sends a large branch, 

 the superior h&morrhoidal. Branches from these hnsmorrhoidals 

 pierce themuscular coat, and anastomose with the rectal twigs of 

 the internal iliac and internal pudic arteries. The inferior mesenteric 

 gives off the colica sinistra, which anastomoses on the descending 

 colon with the colica media above, and with the arteria sigmoidea 

 below. TIi3 colica sinistra lies behind the peritoneum, and in re- 

 moving tlvj kidney throjgh the peritoneum the gland should be reached 

 th? outer sicb of ths descending colon, so that the colica 



