Mesentery

The mesentery is a fold of membranous tissue that arises from the posterior wall of the peritoneal cavity and attaches to the intestinal tract. Within it are the arteries and veins that supply the intestine. The term can be used narrowly to denote just the material that supplies the jejunum and ileum of the small intestine, or broadly to include the right, left and transverse mesocolon, mesoappendix, mesosigmoid and mesorectum.

The human mesentery, also called the mesenteric organ, mainly comprises the small intestinal mesentery, the right, left and transverse mesocolon, mesosigmoid and mesorectum. Conventional teaching has described the mesocolon as a fragmented structure; the small intestinal mesentery, transverse and sigmoid mesocolon all terminate at their insertion into the posterior abdominal wall. Recent advances in gastrointestinal anatomy have demonstrated that the mesenteric organ is actually a single, continuous structure that reaches from the duodenojejunal flexure to the level of the distal mesorectum. This simpler concept has been shown to have significant implications.

Mesentery (zoology)

A mesentery is a membrane inside the body cavity of an animal. The term identifies different structures in different phyla: in vertebrates it is a double fold of the peritoneum enclosing the intestines; in other organisms it forms complete or incomplete partitions of the body cavity, whether that is the coelom or, as in the Anthozoa, the gastrovascular cavity.

The word "mesentery" is derived from the Greek mesos, "in the middle" and enteron, an "intestine".

Vertebrates

In vertebrates, a mesentery is a membrane consisting of a double fold of peritoneum that encloses the intestines and their associated organs and connect them with the dorsal wall of the abdominal cavity. In invertebrates, a mesentery is a support or partition in a body cavity serving a similar function to the mesenteries of vertebrates.

Bilateria

In bilaterally symmetrical organisms there is often a major mesentery separating the two halves of the coelom. In segmented organisms such as earthworms, there are a pair of coelomic cavities in each segment. The mesothelium of the body wall is extended round the central gut to form a mesentery, a longitudinal partition in the sagittal plane. Above the gut is the dorsal mesentery and below the gut, the ventral mesentery. The transverse partition between the separate segments is known as a septum.