The adult diaphragm consists of a muscular skirt and a three-lobed central tendon. Dorsally, the roots of the diaphragm arise from the sides of the upper lumbar vertebrae and form two crura. The right crus forms a sling around the esophageal hiatus. The crura are bridged posteriorly by an arcuate ligament. Beneath this ligament is the aortic hiatus.
Posterolaterally, the diaphragm arises from the lumbocostal arches over the psoas and quadratus lumborum muscles. The remainder of the diaphragmatic skirt arises from the margin of the rib cage and from the sternum anteriorly. The sternal slips are separated slightly from the muscle on either side to allow passage of the internal mammary vessels on their way to become the superior epigastrics in the rectus sheaths. The right lobe of the diaphragm contains the opening for the inferior vena cava.