Peritoneum :: Peritoneum (n.) The smooth serous membrane which lines the cavity of the abdomen, or the whole body cavity when there is no diaphragm, and, turning back, surrounds the viscera, forming a closed, or nearly closed, sac..
Pleuroperitoneum :: Pleuroperitoneum (n.) The pleural and peritoneal membranes, or the membrane lining the body cavity and covering the surface of the inclosed viscera; the peritoneum; -- used especially in the case of those animals in which the body cavity is not divided..