Peritoneum vs. Retroperitoneum — What's the Difference?

The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesothelium supported by a thin layer of connective tissue.

(anatomy) The space in the abdominal cavity behind the peritoneum.

The serous membrane that lines the walls of the abdominal cavity and folds inward to enclose the viscera.

(anatomy) In mammals, the serous membrane lining the cavity of the abdomen and that is folded over the viscera.

(zoology) In animals, the membrane lining the coelom cavity.

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.

A transparent membrane that lines the abdominal cavity in mammals and covers most of the viscera