609 



The Right Colic Artery (a. colica dextra) arises from about the middle of the con- 

 cavity of the superior mesenteric artery, or from a stem common to it and the ileo- 

 colic. It passes to the right behind the peritoneum, and in front of the right 

 internal spermatic or ovarian vessels, the right ureter and the Psoas major, toward 

 the middle of the ascending colon; sometimes the vessel lies at a higher level, 

 and crosses the descending part of the duodenum and the lower end of the right 

 kidney. At the colon it divides into a descending branch, which anastomoses with 

 the ileocolic, and an ascending branch, which anastomoses with the middle colic. 

 These branches form arches, from the convexity of which vessels are distributed 

 to the ascending colon. 





Middle ffemorrhoidal 

 Inferior Hemorrhoidal 



FIQ. 537. The inferior mesenteric artery and its branches. 



The Middle Colic Artery (a. colica media) arises from the superior mesenteric 

 just below the pancreas and, passing downward and forward between the layers of 

 the transverse mesocolon, divides into two branches, right and left; the former 

 anastomoses with the right colic; the latter with the left colic, a branch of the in- 

 ferior mesenteric. The arches thus formed are placed about two fingers' breadth 

 from the transverse colon, to which they distribute branches. 



The inferior mesenteric artery (a. mesenterica inferior} (Fig. 537) supplies the 

 left half of the transverse part of the colon, the whole of the descending and iliac 

 parts of the colon, the sigmoid colon, and the greater part of the rectum. It is 

 smaller than the superior mesenteric, and arises from the aorta, about 3 or 4 cm. 

 39 



