per·i·to·ne·um / ˌperitnˈēəm/ • n. (pl. -ne·ums or -ne·a / -ˈnēə/ ) Anat. the serous membrane lining the cavity of the abdomen and covering the abdominal organs.DERIVATIVES: per·i·to·ne·al / -ˈēəl/ adj.

peritoneum A membrane which lines the inside of the abdomen and covers its contents. The peritoneal ‘cavity’ is an enclosed sac between the lining and the contents, and normally contains only sufficient fluid to lubricate the movement of the loops of the intestines, allowing them to slide freely over each other and against the inside of the abdominal wall. Disease of the stomach, intestines, or appendix which causes leakage or rupture (perforation) can result in dissemination of infected material throughout the cavity, causing peritonitis. Accumulation of fluid in the peritoneal cavity (ascites) occurs along with generalized oedema in conditions such as heart failure or kidney failure.

Stuart Judge

peritoneum (pe-ri-tŏn-ee-ŭm) n. the serous membrane of the abdominal cavity (see illustration). parietal p. the part of the peritoneum that lines the walls of the abdomen. visceral p. the part of the peritoneum that covers the abdominal organs. See also mesentery, omentum.
—peritoneal adj.

peritoneum The thin layer of tissue (see serous membrane) that lines the abdominal cavity of vertebrates and covers the abdominal organs. See also mesentery.

peritoneum XVI. — late L. peritonæum, -ēum — Gr. peritónaion, -eion, sb. use of n. of peritónaios, f. peritonos stretched around, f. PERI- + -tonos stretched.