What is the mediastinum?

• A. The cavity between the lungs that contains the heart and great vessels
• B. The space around the liver
• C. The lining surrounding the lungs
• D. The space inside the heart

Answer: (A)

The mediastinum is the central compartment of the thoracic cavity, located between the two lungs. It contains the heart and great vessels, along with other structures like the trachea and esophagus, and runs from the superior thoracic inlet down to the diaphragmatic hiatus. This makes the description of a cavity between the lungs that contains the heart and great vessels the best fit. The space around the liver is in the abdomen, not the chest; the lining around the lungs is the pleura, which surrounds each lung; and the space inside the heart refers to the heart chambers themselves, which are inside the heart, not in the mediastinum.