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Mediastinum
Gray's Anatomy (1918) plate, public domain
The mediastinum is the central compartment of the chest, the space between the lungs bounded by the breastbone in front and the spine behind. It contains the heart and its great vessels, the thymus, the lower windpipe and its fork, the esophagus, the thoracic duct, major nerves (vagus, phrenic) and chains of lymph nodes. Clinicians divide it into front, middle and back compartments because different diseases favour different compartments.
Key facts
- The heart occupies the middle compartment, wrapped in its pericardium.
- The phrenic nerves cross it to reach the diaphragm — which is why mediastinal tumours can paralyse a diaphragm.
- Its lymph nodes are way-stations for lung drainage and key to lung cancer staging.
- Air escaping into it from a ruptured airway or esophagus (mediastinal emphysema) can track up into the neck.
What can go wrong
Mediastinal problems include tumours (thymomas in front, lymphomas, nerve-sheath tumours behind, germ-cell tumours), enlarged lymph nodes from infection, inflammation (sarcoidosis) or cancer, and infection of the space itself (mediastinitis) — a serious complication after esophageal perforation or heart surgery. Widening on a chest X-ray is the classic first sign and is followed up with CT.
Related conditions
Related procedures & tests
Related symptoms
Watch: related videos
Frequently asked questions
Why is the mediastinum divided into compartments?
Because anatomy predicts pathology: front (anterior) masses are often thymus or lymphoma, middle ones nodes and cysts, back ones nerve tumours — the division guides investigation.
What is EBUS used for here?
Endobronchial ultrasound guides a needle through the airway wall into mediastinal lymph nodes to sample them, mainly for lung cancer staging and diagnosing sarcoidosis or lymphoma.
Educational information only. This atlas explains normal anatomy and describes conditions in general terms; it is not medical advice and does not replace assessment by a qualified clinician. If you have symptoms that worry you, seek medical care.
