mesentery(redirected from mesostenium)
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, multilayered membrane which lines the abdominal cavity, and supports and covers the organs within it. The part of the membrane that lines the abdominal cavity is called the parietal peritoneum.
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(mesenterium), a ligament that suspends and fastens the intestines in the body cavity of humans and animals having a coelom (secondary body cavity). The mesentery arises in the embryo from the internal layers of the lateral plates. These layers, growing together over and under the intestinal canal, form two mesenteries—the dorsal and ventral. Only one of these is usually preserved in the adult organism. In invertebrates (segmented worms) the dorsal mesentery is most often reduced and the ventral one is preserved. In vertebrates the dorsal mesentery is most often preserved. Only fishes of the sturgeon family have a ventral mesentery of the intestinal tract; in remaining vertebrates its vestiges are represented by the falciform ligament of the liver. Each lamina of the mesentery in vertebrates consists of a surface layer of squamous epithelial cells and an internal layer of connective tissue. Between the laminae of the mesentery, in the fatty areolar cellular tissue, are located the lymph nodes and also the nerves passing to the intestines, blood vessels, and lymphatic vessels. On the wide folds of the mesentery, along the intestinal loops, the omenta are formed.
In man the mesentery is a fold of the peritoneum, which covers the crus of each intra-abdominal organ; it is also by means of the mesentery that each of these organs is attached to the wall of the abdominal cavity. Outwardly, the mesentary resembles on old-fashioned collar with gathers, bryzhy (from Polish bryże), from which the Russian term bryzheika originated. Depending on the organ, the mesentery acquires a supplementary designation, for example, mesocolon and mesentery of the uterus. The mesentery is fixed at the place where it emerges from the intestinal wall (mesentery root); the other end, to which the intestines are attached, is free and easily movable. Disease processes that arise in the internal organs (edema, phlebitis, tumors, and so forth) cause intense changes in their mesenteries. Traumas of the mesentery are observed in bruises of the abdomen, strangulated hernias, and puncture wounds of the abdominal cavity.