The abdomen (colloquially called the belly, tummy or midriff) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the trunk. The region occupied by the abdomen is called the abdominal cavity. In arthropods it is the posterior tagma of the body; it follows the thorax or cephalothorax.In humans, the abdomen stretches from the thorax at the thoracic diaphragm to the pelvis at the pelvic brim. The pelvic brim stretches from the lumbosacral joint (the intervertebral disc between L5 and S1) to the pubic symphysis and is the edge of the pelvic inlet. The space above this inlet and under the thoracic diaphragm is termed the abdominal cavity. The boundary of the abdominal cavity is the abdominal wall in the front and the peritoneal surface at the rear.
Structure
In vertebrates, the abdomen is a large body cavity enclosed by the abdominal muscles, at front and to the sides, and by part of the vertebral column at the back. Lower ribs can also enclose ventral and lateral walls. The abdominal cavity is continuous with, and above, the pelvic cavity.
