The abdominal cavity is a large space surrounded by the musculoskeletal abdominal wall, bounded superiorly by the diaphragm and inferiorly by the pelvic inlet. It contains the peritoneal cavity and abdominal viscera.

The abdominal cavity may extend superiorly as high as the 4th intercostal space. Inferiorly, it is continuous with the pelvic cavity, therefore, it may be seen as a part of the abdominopelvic cavity.

The lining of the abdominal cavity is provided by a serous membrane called the peritoneum. The peritoneum covers and supports many of the abdominal organs, as well as serves as a conduit for their nerves, blood vessels, and lymphatic vessels.

The peritoneum consists of two layers: the outer layer (parietal peritoneum) is attached to the abdominal wall, while the inner layer (visceral peritoneum) covers abdominal viscera. A double layer of the visceral peritoneum is formed that attaches to the gastrointestinal tract, and it is called the mesentery. The space between the parietal and visceral layers is called the peritoneal cavity, which is filled with small amount (about 50 mL) of serous fluid.