The peritoneal cavity is a potential space between the parietal and visceral layers of the peritoneum and there are no structures within it. The layer lining the abdominal wall, the pelvic wall and pelvic viscera, and the inferior surface of the diaphragm is the parietal peritoneum and the layer lining the surface of the organs is called the visceral peritoneum. Just as in the pleural and pericardial cavities, the peritoneal cavity contains a film of serous fluid that lubricates the peritoneal surfaces and allows free movement of the viscera.

As with the pleural and pericardial cavities, the peritoneal cavity surrounds, but does not contain, most of the abdominal organs. Most, but not all, of the organs associated with the GI tract are suspended "within" the peritoneal cavity by connections to the posterior abdominal wall called mesenteries.