The peritoneum is a thin membrane that lines the abdominal cavity and covers the organs within it. It consists of two layers: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelops the organs. This membrane helps protect the organs and provides a smooth surface for them to move against each other. Additionally, the peritoneum plays a role in the immune response and fluid balance in the abdomen. It contains blood vessels, lymphatics, and nerves, contributing to the overall health of the abdominal organs, including the stomach, liver, and intestines.