THE ABDOMINAL AORTA 665 



the layers of the mesentery. (See the description of the vascular loops in the 

 section upon the Intestines.) 



The ileocolic artery (a. ileocolicd) is the lowest branch given oft' from the con- 

 cavity of the superior mesenteric artery. It descends between the layers of 

 the mesentery to the right iliac fossa, where it divides into two branches. Of 

 these, the inferior division anastomoses with the termination of the superior mesen- 

 teric artery, forming with it an arch, from the convexity of which branches 

 proceed to supply the termination of the ileum, the cecum, the vermiform appen- 

 dix, and the ileocecal valve.. The superior division anastomoses with the 

 colic and .supplies the commencement, of the colon. 



ILEOCOLIC ARTERY 

 AND VEIN 



POSTERIOR 



ILEOCECAL 



ARTERY 



AND VEIN 



ILIAC BRANCH 



APPENDICULAR 



ARTERY AND 



VEIN 



"^ 



\l ASCENDING 



COLON 



FIG. 470. Arteries and veins of the cecum and vermiform appendix seen from behind. (Poirier and Charpy.) 



The descending branch of the ileocolic runs toward the upper border of the 

 ileocecal junction and gives off the following branches: 



(a) Colic, which passes upward on the ascending colon; (6) anterior and 

 posterior cecal (or ileocecal), which are distributed to the front and back of the 

 cecum; (c) appendicular (a. appendicularis] , which passes downward behind the 

 terminal part of the ileum and runs in the mesoappendix close to its free margin 

 for the supply of the appendix; and (d) ileal, which runs upward and to the left 

 on the terminal part of the ileum and anastomoses with the termination of the 

 superior mesenteric (Fig. 470). 



The right colic artery (a. colica dextra) arises from about the middle of the 

 concavity of the superior mesenteric artery; it passes to the right behind the 

 peritoneum to the middle of the ascending colon, and divides into two branches 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. 



The middle colic artery (a. colica media} arises from the upper part of the 

 concavity of the superior mesenteric, and, passing downward and forward between 

 the layers of the transverse mesocolon, divides into two branches, the one on the 

 right side anastomosing with the right colic; that on the left side, with the left 

 colic, a branch of the inferior mesenteric. From the arches formed by their 

 anastomosis branches are distributed to the transverse colon. The branches of 

 this vessel lie between the two lavers of the transverse mesocolon. 



