peritoneums

The peritoneum is a continuous serous membrane that lines the abdominal cavity (parietal peritoneum) and covers most abdominal organs (visceral peritoneum). It forms a single, closed cavity—the peritoneal cavity—that normally contains a small amount of lubricating fluid to reduce friction between moving organs. The standard plural is peritonea; peritoneums is nonstandard but occasionally encountered.

The peritoneum forms several folds and layers, including mesenteries, omenta, and ligaments, which suspend and anchor organs to the posterior abdominal wall or to each other. It creates two main spaces: the greater sac and the smaller lesser sac (omental bursa) behind the stomach.

Innervation differs by layer: the parietal peritoneum is supplied by somatic nerves and pain is well localized, whereas the visceral peritoneum is supplied by autonomic nerves and sensations are dull. Functions include production and resorption of peritoneal fluid, lubrication of surfaces, filtration and immune defense, and providing a route for blood vessels, lymphatics, and nerves to reach abdominal organs.

Clinically, the peritoneum is central to conditions such as peritonitis (inflammation of the peritoneum), ascites (accumulation of fluid), and peritoneal carcinomatosis. It is also used therapeutically in peritoneal dialysis, where the peritoneal membrane acts as a dialysis surface. Adhesions can form after infection or surgery, potentially affecting organ movement and function.

Embryologically, the peritoneum arises from coelomic mesoderm during gut formation, creating the peritoneal cavity as the gut tubes rotate and fuse with the posterior abdominal wall. The peritoneum thus forms the serous lining that remains in the adult.