What structure surrounds the abdominal cavity?

The peritoneum is a vital structure that surrounds the abdominal cavity, acting as a protective membrane. It consists of two layers: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelops the abdominal organs. This serous membrane not only provides a barrier to protect the organs but also facilitates movement and serves as a conduit for blood vessels, lymphatics, and nerves to the organs within the abdominal cavity.

In contrast, the thoracic cavity contains the heart and lungs and is separated from the abdominal cavity by the diaphragm. The pericardial cavity specifically encases the heart and is not involved with the abdominal structures. The pleural cavity surrounds each lung and is also separate from the abdominal region. Thus, the peritoneum uniquely fulfills the role of enclosing the abdominal cavity and its contents.