410 ABDOMINAL AORTA. 



(d) The left yastro-epiploic artery runs from left to right along the great 

 curvature of the stomach, supplying branches to both surfaces of the 

 stomach and to the omentum on the left side, and inosculates with the 

 right gastro-epiploic branch from the hepatic artery. 



II. SUPERIOR MESENTERIC ARTERY. 



The superior mesenteric, an artery of large size, supplies the whole of the 

 small intestine beyond the duodenum, and half of the great intestine. It 

 arises from the fore part of the aorta, a little below the cosliac artery. For 

 a short space this artery is covered by the pancreas ; on emerging from 

 below that gland it descends in front of the duodenum near the end, and is 

 thence continued between the layers of the mesentery. The splenic vein 

 crosses over its root. In the mesentery the artery at first passes downwards 

 and to the left side, but afterwards turns towards the right iliac fossa, 

 opposite to which it inosculates with its own ileo-colic branch. 



BRANCHES. (a) The inferior pancreaiico- duodenal, given off under cover 

 of the pancreas, runs along the concave border of the duodenum, and joins 

 with the pancreatico-duodenal artery. 



(6) The rami intestini tennis, or intestinal branches, supplying the jejunum 

 and ileum, spring from the convex or left side of the vessel. They are 

 usually twelve or more in number, and are all included between the layers 

 of the mesentery. They run parallel to one another for some distance, 

 and then divide into two branches, each of which forms an arch with the 

 neighbouring branch. From the first set of arches other branches issue, 

 which divide and communicate in the same way, until finally, after forming 

 four or five such tiers of arches, each smaller than the other, the ultimate 

 divisions of the vessels proceed directly to the intestine, spreading upon 

 both sides, and ramifying in its coats. 



(c) The colic branches arise from the right or concave side of the artery, 

 and are three in number. 



1. The ileo-colic artery, the first in order from below upwards, inclines 

 downwards and to the right side, towards the ileo-colic valve, near which it 

 divides into two branches : one of these descends to inosculate with the 

 termination of the mesenteric artery itself, and to form an arch, from the 

 convexity of which branches proceed to supply the junction of the small 

 with the large intestine, and the csecum and its appendix ; the other divi- 

 sion ascends and inosculates with the next mentioned branch. The ileo- 

 colic artery is not always distinct from the termination of the superior 

 mesenteric. 



2. The right colic artery passes transversely towards the right side, 

 beneath the peritoneum, to the middle of the ascending colon, opposite to 

 which it divides into two branches, of which one descends to communicate 

 with the ileo-colic artery, whilst the other ascends to join in an arch with 

 the middle colic. This artery and the ileo-colic often arise by a common 

 trunk. 



3. The middle colic artery passes upwards between the layers of the 

 mesocolon towards the transverse colon, and divides in a manner exactly 

 similar to that of the vessels just noticed. One of its branches inclines to 

 the right, where it inosculates with the preceding vessel ; the other descends 

 to the left side, and maintains a similar communication with the left colic 

 branch, derived from the inferior mesenteric artery. From the arches of 

 inosculation thus formed, small branches pass to the colon for the supply of 

 its coats. 



