|Mediastinum. The division between superior and inferior is at the sternal angle.|
|Gray's||subject #239 1090|
The mediastinum is a non-delineated group of structures in the thorax, surrounded by loose connective tissue. It is the central compartment of the thoracic cavity. It contains the heart, the great vessels of the heart, esophagus, trachea, phrenic nerve, cardiac nerve, thoracic duct, thymus, and lymph nodes of the central chest.
The mediastinum lies between the right and left pleura in and near the median sagittal plane of the chest. It extends from the sternum in front to the vertebral column behind, and contains all the thoracic viscera except the lungs. It may be divided for purposes of description into two parts:
Note that clinical radiologists and anatomists categorize the mediastinum in slightly different ways.
The mediastinum is frequently the site of involvement of various tumors.
Mediastinitis is inflammation of the tissues in the mediastinum, usually bacterial and due to rupture of organs in the mediastinum. As the infection can progress very quickly, this is a serious condition.
Pneumomediastinum is the presence of air in the mediastinum, which in some cases can lead to pneumothorax, pneumoperitoneum, and pneumopericardium if left untreated. However, that does not always occur and sometimes those conditions are actually the cause, not the result, of pneumomediastinum. These conditions frequently accompany Boerhaave's syndrome, or spontaneous esophageal rupture.
There are many diseases that can present with a widened mediastinum (usually found via a chest x-ray). The classic is aortic rupture or thoracic vertebrae fracture due to trauma. With infectious etiologies, a widened mediastinum is a classic hallmark sign of anthrax infection.