- Mediastinum (L. middle septum): median septal compartment of the thoracic cavity between the two pleural cavities, occupying its central compartment.
- Contains all thoracic viscera except the lungs.
- Not a rigid partition: consisting mainly of hollow, fluid- or air-filled viscera bound by loose connective tissue, it is a dynamic, pliable and mobile septum in the living body.
Boundaries and Contents of the Mediastinum
Boundaries of the mediastinum
Boundary
Anterior
- Structure
- Sternum
Posterior
- Structure
- Vertebral column (bodies of thoracic vertebrae and intervertebral discs)
Superior
- Structure
- Superior thoracic aperture
Inferior
- Structure
- Diaphragm
Each side
- Structure
- Mediastinal pleura