AskDefine | Define mediastinum

Dictionary Definition

mediastinum n : the part of the thoracic cavity between the lungs that contains the heart and aorta and esophagus and trachea and thymus [also: mediastina (pl)]

User Contributed Dictionary



  1. The region in mammals between the pleural sacs, containing the heart and all of the thoracic viscera except the lungs.


  • German: Mediastinum

Extensive Definition

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, 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:
  • an upper portion, above the upper level of the pericardium, which is named the superior mediastinum with its superior limit at the superior thoracic opening and its inferior limit at the plane from the sternal angle to the disc of T4-T5 (Plane of Ludwig);
  • and a lower portion, below the upper level of the pericardium. This lower portion is again subdivided into three parts, viz.:
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

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.
A widened mediastinum (usually found via a chest x-ray) is a classic hallmark sign of anthrax posioning. At this point, the disease is typically fatal.

External links

  • - "Divisions of the mediastinum."
  • - "The anatomical divisions of the inferior mediastinum."
  • - "Subdivisions of the Thoracic Cavity"
mediastinum in Breton: Mediastinum
mediastinum in Catalan: Mediastí (tòrax)
mediastinum in German: Mediastinum
mediastinum in Spanish: Mediastino
mediastinum in French: Médiastin
mediastinum in Indonesian: Mediastinum
mediastinum in Italian: Mediastino
mediastinum in Latin: Mediastinum
mediastinum in Hungarian: Mediastinum
mediastinum in Dutch: Mediastinum
mediastinum in Japanese: 縦隔
mediastinum in Polish: Śródpiersie
mediastinum in Portuguese: Mediastino
mediastinum in Finnish: Välikarsina
mediastinum in Swedish: Mediastinum
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