Mesentery
From IKE
Mesentery is a thin, double-layered membrane which reflects from the lining (parietal peritoneum) of the coelom, then splits to surround the gut tube as visceral peritoneum. At first, much of the primitive gut is suspended in the intraembryonic coelom by mesentery which contains the blood vessels, nerves and lymphatics of the gut. If the mesentary fuses, it is said to have undergone zygosis. A dorsal mesentery is found in association with all three parts of the gut tube, whereas a ventral mesentery is associated only with the foregut and its derivatives.
The dorsal mesentery is a double-fold of peritoneum that suspends the gastrointestinal tract from the posterior wall of the abdominal cavity in early development. It is continuous with the parietal peritoneum lining the cavity, and conveys blood vessels, lymphatics and nerves to and from the gastrointestinal tract. During development, parts of the dorsal mesentery may become fused with the parietal peritoneum of the posterior abdominal wall in the process called zygosis. If this occurs, the affected mesentery is then said to be (secondarily) retroperitoneal or fixed. During development, the dorsal mesentery associated with the stomach (dorsal mesogastrium) becomes elongated, forming a recess of the peritoneal cavity, located behind the stomach. This is the lesser sac (omental bursa).
The ventral mesentery also suspends the derivatives of the caudal part of the foregut.
