Abomasum(redirected from abomasus)
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the fourth and last part of the multicompartmental stomach of ruminants, corresponding to the simple uncompartmental stomach of most mammals. The abomasum is connected to the omasum (third stomach) and the duodenum. The mucous membrane of the abomasum is covered by prismatic epithelium and contains fundic, pyloric, and cardiac glands. It forms 13 or 14 long folds, which enlarge its surface. In young animals the mucous membrane of the abomasum produces rennin. The muscular membrane of the abomasum consists of external longitudinal and internal circular layers. Food is digested in the abomasum by gastric juice.