the membranes, or one of the membranes (consisting of a fold of the peritoneum and inclosed tissues), which connect the intestines and their appendages with the dorsal wall of the abdominal cavity. the mesentery proper is connected with the jejunum and ilium, the other mesenteries being called mesocaecum, mesocolon, mesorectum, etc.-one of the vertical muscular radiating partitions which divide the body cavity of anthozoa into chambers.