The abdominal cavity is bounded above by the diaphragm. The roots of the diaphragm originate along the lateral borders of the upper lumbar vertebrae. The esophageal hiatus is comprised of muscle predominantly from the right crus. The aortic hiatus is formed by the crossing of the two crura.
The parietal peritoneum conforms to the contours of the endoabdominal fascia. The shape of this envelope is bulbous beneath the diaphragms, flattened by spinal column and psoas muscles in the mid-abdomen and takes a sharp posterior turn into the sacral hollow of the pelvis. The peritoneum is loosely adherent to transversalis fascia, the interspace contains pre-peritoneal fat, and is easily peeled apart