Abdomen

The abdomen is a body region which is cylindrical in shape and is situated between the thorax (above) and the pelvis (below). The abdominal cavity extends from the diaphragm above, to the pelvic inlet or pelvic brim below. In fact, the abdominal and pelvic cavities are continuous entities, forming one large abdominopelvic peritoneal cavity. Outside, the abdominal walls continue with the pelvic walls.

The abdomen houses most of the viscera of digestive system, the spleen and various components of the urogenital system. Some are suspended into the abdominal cavity by mesentery, hence called intraperitoneal. While others are retroperitoneal and lie outside the abdominal cavity, i.e. between the parietal peritoneum and the abdominal wall. The abdomen also helps in breathing. The contraction of abdominal walls raises the intra-abdominal pressure which is useful in expiration and voiding the elements of bladder and the rectum. Raised intra-abdominal pressure also helps in child birth.