Jejunum and Ileum

The jejunum and ileum is slung from the posterior abdominal wall by the mesentery of the small intestines and, therefore, is extremely mobile. The mesentery of the small intestine arises from the root of the mesentery which extends from the duodenojejunal flexure to the ileocecal junction. The jejunum is about 2.5m (8ft) long and passes imperceptibly into the ileum, which is about 4m (12ft) long. this part of the small intestine occupies a central position in the abdominal cavity, below the liver and the stomach, and behind the transverse mesocolon, the transverse colon and the greater omentum. The lowest coils of the intestine lie in the pelvic cavity. The purple dotted line in the lower image is an arbitrary line that can be used to separate the jejunum which is to the upward left of the line and the ileum which is to the downward and right of the line.

Blood Supply to Ileum and Jejunum

The ileum and jejunum are supplied by the superior mesenteric artery and its intestinal branches. The branches are rather special in that small arcades are formed and from the arcades, the straight vessels, vasa recta arise and supply the intestine. These straight vessels are end arteries and if they should be occluded, the part of the intestine supplied by them will die. One way to tell the ileum from the jejunum, other than by general location, is that there are more layers of arcades before the vasa recta are given off, in the ileum.

Duodenum

Large Intestine

This is copyrighted©1999 by Wesley Norman, PhD