554 



THE BLOOD-VASCULAR SYSTEM. 



forward and downward to the left side, tlie concavity backward and upward to the 

 right. It is accompanied by the superior mesenteric vein, and is surrounded 

 by the superior mesenteric plexus of nerves. Its branches are the 



Inferior Pancreatico-duodenal. 

 Vasa Intestini Tenuis. 



Colica Media. 



Ileo-colic. 

 Colica Dextra. 



FIG. 310. The superior mesenteric artery and its branches. 



The inferior pancreatico-duodenal is given off from the superior mesenteric, or 

 from its first intestinal branch behind the pancreas. It courses to the right be- 

 tween the head of the pancreas and duodenum, and then ascends to anastomose 

 with the superior pancreatico-duodenal artery. It distributes branches to the head 

 of the pancreas and to the transverse and descending portions of the duodenum. 



The vasa intestini tenuis arise from the convex side of the superior mesenteric 

 artery. They are usually from twelve to fifteen in number, and are distributed to 

 the jejunum and ileum. They run parallel with one another between the layers 

 of the mesentery, each vessel dividing into two branches, which unite with a sim- 

 ilar branch on each side, forming a series of arches the convexities of which are 

 directed toward the intestine. From this first set of arches branches arise, 

 Avhich 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 fourth, or even fifth, 

 series of arches is constituted, diminishing in size the nearer they approach the 



