The peritoneal cavity is a space within the abdomen that contains the abdominal organs. It is lined by a thin membrane called the peritoneum, which helps protect and support these organs. This cavity allows for movement and expansion of the organs during digestion and other bodily functions. The peritoneal cavity also plays a role in the immune response and fluid balance. It can be affected by conditions such as peritonitis, an inflammation often caused by infection, and can be accessed for medical procedures like peritoneal dialysis, which helps remove waste from the body in patients with kidney failure.