610 ANGIOLOGY 



above its division into the common iliacs and close to the lower border of 

 inferior part of the duodenum. It passes downward posterior to the peritoneum, 

 lying at first anterior to and then on the left side of the aorta. It crosses the 

 left common iliac artery and is continued into the lesser pelvis under the name of 

 the superior hemorrhoidal artery, which descends between the two layers of the 

 sigmoid mesocolon and ends on the upper part of the rectum. 

 Branches. Its branches are: 



Left Colic. Sigmoid. Superior Hemorrhoidal. 



The Left Colic Artery (a. colica sinistra) runs to the left behind the peritoneum 

 and in front of the Psoas major, and after a short, but variable, course divides 

 into an ascending and a descending branch; the stem of the artery or its branches 

 cross the left ureter and left internal spermatic vessels. The ascending branch 

 crosses in front of the left kidney and ends, between the two layers of the transverse 

 mesocolon, by anastomosing with the middle colic artery; the descending branch 

 anastomoses with the highest sigmoid artery. From the arches formed by these 

 anastomoses branches are distributed to the descending colon and the left part 

 of the transverse colon. 



The Sigmoid Arteries (aa. sigmoidece) (Fig. 538), two or three in number, run 

 obliquely downward and to the left behind the peritoneum and in front of the 

 Psoas major, ureter, and internal spermatic vessels. Their branches supply the lower 

 part of the descending colon, the iliac colon, and the sigmoid or pelvic colon ; anasto- 

 mosing above with the left colic, and below with the superior hemorrhoidal artery. 



The Superior Hemorrhoidal Artery (a. hcemorrhoidalis superior) (Fig. 538), the 

 continuation of the inferior mesenteric, descends into the pelvis between the layers 

 of the mesentery of the sigmoid colon, crossing, in its course, the left common 

 iliac vessels. It divides, opposite the third sacral vertebra, into two branches, 

 which descend one on either side of the rectum, and about 10 or 12 cm. from the 

 anus break up into several small branches. These pierce the muscular coat of the 

 bowel and run downward, as straight vessels, placed at regular intervals from each 

 other in the wall of the gut between its muscular and mucous coats, to the level 

 of the Sphincter ani internus ; here they form a series of loops around the lower end 

 of the rectum, and communicate with the middle hemorrhoidal branches of the 

 hypogastric, and with the inferior hemorrhoidal branches of the internal pudendal. 



The middle suprarenal arteries (aa. suprarenales media; middle capsular arteries; 

 suprarenal arteries) are two small vessels which arise, one from either side of the 

 aorta, opposite the superior mesenteric artery. They pass lateralward and slightly 

 upward, over the crura of the diaphragm, to the suprarenal glands, where they 

 anastomose with suprarenal branches of the inferior phrenic and renal arteries. In 

 the fetus these arteries are of large size. 



The renal arteries (aa. renales] (Fig. 531), are two large trunks, which arise 

 from the side of the aorta, immediately below the superior mesenteric artery. 

 Each is directed across the crus of the diaphragm, so as to form nearly a right 

 angle with the aorta. The right is longer than the left, on account of the position 

 of the aorta ; it passes behind the inferior vena cava, the right renal vein, the head 

 of the pancreas, and the descending part of the duodenum. The left is somewhat 

 higher than the right; it lies behind the left renal vein, the body of the pancreas 

 and the lienal vein, and is crossed by the inferior mesenteric vein. Before reaching 

 the hilus of the, kidney, each artery divides into four or five branches; the greater 

 number of these lie between the renal vein and ureter, the vein being in front, 

 the ureter behind, but one or more branches are usually situated behind the ureter. 

 Each vessel gives off some small inferior suprarenal branches to the suprarenal 

 gland, the ureter, and the surrounding cellular tissue and muscles. One or two 

 accessory renal arteries are frequently found, more especially on the left side 



