Now we'll move on to look at the artery of the mid-gut, the superior mesenteric artery. It supplies the distal duodenum, the jejuno-ileum, the ascending colon and part of the transverse colon. The superior mesenteric arises from the aorta just below the celiac trunk. To see it we'll look at a dissection similar to the last one.
Here's the pancreas, here's the celiac trunk, arising from the aorta. Here's the superior mesenteric artery. It arises up here beneath the pancreas. We'll remove this part of the pancreas to see it.
Here's the origin of the superior mesenteric artery. It runs almost straight downward, with a large vein in front of it, the splenic vein, and a large vein behind it, the left renal vein, both of which are empty here.
It gives off branches that supply the pancreas and duodenum, then emerges from beneath the pancreas, which we'll restore to its intact state. The superior mesenteric artery emerges here from beneath the neck of the pancreas, along with the superior mesenteric vein. It passes in front of the uncinate process of the pancreas, which is under here, and in front of the third part of the duodenum,
As it does so it gives off numerous branches. Some of these enter the mesentery, which has been removed here, two run down and to the right in the retroperitoneum, and one passes upward, to enter the transverse mesocolon.
To see all these branches better we'll go to an earlier stage in the dissection, in which all the viscera are intact. To get to where we were just now, we'll lift up the dependent part of the greater omentum, and with it the transverse colon. We'll dissect in this area to see the superior mesenteric artery and its branches.
Here's the superior mesenteric artery. Here's the duodenum beneath it. These branches, that pass downwards and to the left, fan out to supply the jejuno-ileum. This one, the ileo-colic, goes toward the cecum; these two, the right colic and middle colic go to the ascending colon and the transverse colon respectively. As they approach the intestine the superior mesenteric branches rejoin to form a set of vascular arcades that run close to the intestine along its length.
Next we'll look at the inferior mesenteric artery, the artery of the hind-gut. It supplies the distal colon and the rectum. Its origin from the aorta is below the pancreas and duodenum, at the level of L3. To see it we'll go to an earlier stage of the same dissection, and displace the jejuno-ileum to the right. Here's the transverse mesocolon, here are the descending colon, and sigmoid colon.
We'll dissect in this area to expose the inferior mesenteric artery and its branches. Here's the distal part of the duodenum. Here's the aorta. It bifurcates down here.
Here's the inferior mesenteric artery arising from the aorta. It passes downwards, giving off these branches to the colon. This one is the left colic artery, which supplies the ascending colon and the distal part of the transverse colon. It anastomoses with the middle colic artery, forming an arcade in the transverse mesocolon.
These branches of the inferior mesenteric artery supply the sigmoid colon. This last branch is the superior rectal artery. It runs down into the pelvis, to supply the upper part of the rectum.
The lower parts of the rectum are supplied by branches of the internal iliac artery.