Life Science Encyclopedia

The mediastinum is a non-delineated group of structures in the thorax (chest), 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, thymus, and lymph nodes of the central chest.

Anatomy

The mediastinum lies between the right and left pleuræ 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:

• an upper portion, above the upper level of the pericardium, which is named the superior mediastinum;
• and a lower portion, below the upper level of the pericardium. This lower portion is again subdivided into three parts, viz.:
  • that in front of the pericardium, the anterior mediastinum;
  • that containing the pericardium and its contents, the middle mediastinum;
  • and that behind the pericardium, the posterior mediastinum.

It is surrounded by the chest wall anteriorly, the lungs laterally and the spine posteriorly. It is continuous with the loose connective tissue of the neck, and extends inferiorly onto the diaphragm.

Note that clinical radiologists and anatomists categorize the mediastinum in slightly different ways.

Role in disease

Main article: mediastinal tumor

The mediastinum frequently is 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 can lead to pneumothorax, pneumoperitoneum, and pneumopericardium if left untreated in some cases. However, that does not always happen and sometimes those conditions actually are the cause, not the result, of pneumomediastinum.

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

See also

• Widened mediastinum
• Mediastinum testis (unrelated structure in the scrotum)
• Mediastinal germ cell tumor
• Mediastinitis

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.