The Branches From The Convexity are fifteen to twenty in number: they are contained between the layers of the mesentery, and destined for the ileum, jejunum, and third portion of the duodenum. Each of them, after a short course, divides into two branches, which anastomose with the branches of the adjacent arteries, so as to form a series of arches. From the convexities of these, smaller arteries arise, which likewise bifurcate, forming a second and lesser series of arches with those adjacent; and in the same manner a third and fourth, and, in some cases, a fifth series is formed, gradually approaching the intestine, and diminishing in size : the entire arrangement presents an areolar appearance in the mesentery; and when the ultimate branches (which advance in straight lines) reach the intestine for which they are destined, they encircle it, and form a delicate vascular stratum in its sub-mcuous areolar tissue.

The Branches from the Concavity are three in number, viz.:

Colica Media, Colica Dextra, and Ileo-Colic.

These arteries are considerably longer than the preceding: they are contained between the layers of the mesocolon, and are destined to supply the arch of the colon, the right or ascending colon, and the caecum, with part of the ileum.

The Colica Media

The Colica Media goes horizontally forward between the laminae of the transverse mesocolon, and soon divides into a right and a left branch; the former of which anastomoses with the superior branch of the colica dextra, and the latter with the superior branch of the colica sinistra, which is a branch of the inferior mesenteric: this artery supplies the arch or middle portion of the colon.

Fig. 37. Distribution of the Superior Mesenteric Artery.

1, Superior Mesenteric Artery. 2. Jejunal and Ileal Arteries. 3, Ileocolic Artery. 4, Right Colic. 5, Middle Colic Artery. 6, Duodenal Artery, a. Small Intestine turned to the left. 6, Large Intestine, c, Pancreas.