The peritoneal cavity is a space within the abdomen that contains various organs, including the stomach, intestines, and liver. It is lined by a thin membrane called the peritoneum, which helps protect and support these organs while allowing them to move freely during digestion. This cavity plays a crucial role in the body's immune response and fluid balance. It can also be involved in medical conditions such as peritonitis, an inflammation of the peritoneum, which can occur due to infection or injury. Understanding the peritoneal cavity is important for diagnosing and treating abdominal diseases.