 Abdomen, the abdomen less formally called the belly, stomach, tummy or midriff constitutes a part of the body between the thorax chest and pelvis, in humans and in other vertebrates. The region occupied by the abdomen is termed the abdominal cavity. In arthropods it is the posterior tagma of the body, it follows the thorax or cephalothorax. 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 that 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.