The Mediastinum

This is the region of the thoracic cavity between the two pleural cavities. It is what is left after the lungs and the pleuca have been removed from the thoracic cavity.

Extents and boundaries

• The mediastinum extends from the superior thoracic inlet superiorly, to the thoracic diaphragm inferiorly .
  
  
• Boundaries
  
  Anteriorly - sternum and costal cartilages
  
  Posteriorly - thoracic vertebrae and their associated intervertebral discs and anterior longitudinal ligaments.
  
  Laterally- pleural cavities, containing the lungs.
  
  
• The root of the lungs connects the mediastinum to the lungs.

The mediastinum is divided by a plane passing from the sternal angle to T4-T5 into:

• Superior mediastinum and
• The inferior mediastinum (2,3.4)

The inferior mediastinum is further subdivided into three regions namely:

• Anterior mediastinum
• Middle mediastinum
• Posterior mediastinum

These divisions are for descriptive purposes, merge into each other inpercleptibly. There are no distinct boundaries between them.