The mediastinum is a broad central partition that separates the two laterally placed pleural cavities (Fig. 3.55). It extends: from the sternum to the bodies of the vertebrae, and from the superior thoracic aperture to the diaphragm (Fig. 3.56).
The mediastinum contains the thymus gland, the pericardial sac, the heart, the trachea, and the major arteries and veins.