In
anatomy, the
mesentery is the double layer of
peritoneum that suspends the
jejunum and
ileum from the posterior wall of the
abdomen. Its meaning, however, is frequently extended to include double layers of peritoneum connecting various components of the abdominal cavity.
Mesentery (proper)
The mesentery proper (i.e. the original definition) refers to the peritoneum responsible for connecting the
jejunum and
ileum, parts of the
small intestine, to the back wall of the abdomen. Between the two sheets of peritoneum are blood vessels, lymph vessels, and
nerves. This allows these parts of the small intestine to move relatively freely within the abdominopelvic cavity. The brain, however, cannot map sensation accurately, so sensation is usually referred to the midline, an example of
referred pain.
Development
The mesentery is derived from what is known in the embryo as the
dorsal mesentery. The dorsal mesentery is larger than the
ventral mesentery, which gradually becomes other parts of the peritoneum. Most parts of the ventral mesentery are associated with the liver.
Mesentery (general)
Mesenteries are composed of two layers of peritoneum. The peritoneum that lies on the walls of the abdominopelvic cavity (parietal peritoneum) invaginates at certain parts, with an organ inside this invagination. This invaginated peritoneum (visceral peritoneum) will often surround all but a part of the organ ("bare area"), through which the organ transmits blood vessels and nerves. If this organ is invaginated far enough into the peritoneum, the visceral peritoneum will come in contact with itself, forming the organ's mesentery.
Mesenteries in the body:
Pathology
A lack of blood-supply to the mesentery causes
mesenteric ischemia.
Invertebrate anatomy
In
invertebrates, the term
mesentery is used for any tissue that divides the body cavity (
coelom) into partitions.
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