The mediastinum is a broad central partition that separates the two laterally placed pleural. It extends from the sternum to the bodies of the vertebrae and from the superior thoracic aperture to the diaphragm.
The mediastinum contains the thymus gland, the pericardial sac, the heart, the trachea, and the major arteries and veins.
Additionally, the mediastinum serves as a passageway for structures such as the esophagus, thoracic duct, and various components of the nervous system as they traverse the thorax on their way to the abdomen.