502 



ARTERIES. 



with a similar branch on each side, forming a series of arches, the convexities 

 of which are directed towards the intestine. From this first set of arches 

 branches arise, which again unite with similar branches from either side, and 

 thus a second series of arches is formed ; and from these latter, a third, and a 



Fig. 292. The Superior Mesenteric Artery and Branches. 



fourth, or even fifth series of arches are constituted, diminishing in size th< 

 nearer they approach the intestine. From the terminal arches numerous small 

 straight vessels arise, which encircle the intestine, upon which they are dis- 

 tributed, ramifying thickly between its coats. 



The ileo-colic artery is the lowest branch given off from the concavity 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 in- 

 ferior one inosculates with the lowest branches of the vasa intestini tenuis, 

 from the convexity of which branches proceed to supply the termination of 

 the ileum, the ccecum and appendix cocci, and the ileo-coecal valve. The 

 superior division inosculates with the colica dextra, and supplies the commence 

 ment of the colon. 



The colica dextra arises from about the middle of the concavity of the supe- 

 rior mesenteric artery, and passing beneath the peritoneum to the middle of 

 the ascending colon, divides into two branches; a descending branch, which 

 inosculates with the ileo-colic; and an ascending branch, which anastomoses 

 with the colica media. These branches form arches, from the convexity of 



