As the diaphragm contracts, the height of the domes decreases and the volume of the thorax increases.
The esophagus and inferior vena cava penetrate the diaphragm; the aorta passes posterior to the diaphragm.
The mediastinum is a thick midline partition that extends from the sternum anteriorly to the thoracic vertebrae posteriorly, and from the superior thoracic aperture to the inferior thoracic aperture.