Surrounded by loose connective tissue, it is a region that contains vital organs and structures within the thorax, namely the heart and its vessels, the esophagus, the trachea, the vagus, phrenic and cardiac nerves, the thoracic duct, the thymus and the lymph nodes of the central chest.

It is surrounded by the chest wall in front, the lungs to the sides and the spine at the back.

Pneumomediastinum is the presence of air in the mediastinum, which in some cases can lead to pneumothorax, pneumoperitoneum, and pneumopericardium if left untreated.

These conditions frequently accompany Boerhaave syndrome, or spontaneous esophageal rupture.

[11] A widened mediastinum can be indicative of several pathologies:[12][13] This article incorporates text in the public domain from page 1090 of the 20th edition of Gray's Anatomy (1918)