The fan-shaped muscle of the diaphragm arises from the internal circumference of the thorax, with attachments to the sternum, the lower six or seven ribs, and the lumbar vertebral bodies. The muscle fibers also attach posteriorly to the aponeurotic arch of the ligamentum arcuatum externum, which overrides the psoas and quadratus lumborum muscles (Fig. 149-1). Laterally, the fibers of the diaphragm interdigitate with slips from the transversalis muscle of the abdomen to originate from the ribs.1 The right crus is larger and longer than the left and arises from the bodies of the upper three or four lumbar vertebrae. The left crus arises from the upper two lumbar vertebral bodies.
The muscle fibers of the diaphragm originate from the posterior lumbar spine (arcuate ligaments) and curve upward to form an aponeurotic sheath known as the central tendon. Several thoracic organs and vessels pass through apertures in the diaphragmatic surface.
There are three natural openings within the diaphragm (Fig. 149-2). The aortic opening is the most posterior of the three and is formed from fibers comprising the right and left diaphragmatic crura.1 This tunnel is actually behind the diaphragm, not within it, and contains the aorta, azygos vein, and thoracic duct. The esophageal hiatus is slightly more ventral in relation to the aortic hiatus and consists of fibers passing between the aorta and the esophagus toward the right crus, as well as fibers converging on the pericardial tendon. The opening of the inferior vena cava lies within the confluence of the tendons of the right hemithorax and the tendon beneath the pericardium.
Abdominal surface of the diaphragm with three natural openings.
The muscular diaphragm acts as a boundary between the positive pressure abdominal cavity and the negative pressure thoracic cavity. Although diaphragmatic disease is infrequent, exposure to the diaphragm is commonplace, because it is visualized during every thoracic surgical procedure and most intraabdominal operations. Therefore the basic principles advocated by this chapter can be verified in the operating room. The diaphragm makes a good fence, but neighbors on both sides of that fence should know its anatomy, physiology, and surgical principles of resection and repair.
Phrenic Nerve and Vessel Branches in the Diaphragm
A number of incisions in the diaphragm are possible once the location of the nerve and vessel branches have been learned. These structures frequently lie within the muscle itself and are not seen on the cranial surface of the structure. Therefore, the concept of a neurovascular “manacle” around the junction of the central tendon to the muscle is a very helpful visual mnemonic.
The phrenic nerve originates from the C3, C4, and ...