The mediastinum is the area of the thoracic cavity between which structures?

• A. Between the diaphragm and lungs
• B. Between the heart and lungs
• C. Between the lungs
• D. In the pleural spaces

Answer: (C)

The mediastinum is the central thoracic compartment that lies between the two lungs. It extends from the sternum and thoracic inlet anteriorly and superiorly down to the diaphragm posteriorly, serving as the space that contains the heart and other midline structures. This central position explains why the lungs form the lateral borders of the mediastinal space.

Think of the lungs as flanking the mediastinum; the heart sits inside this central area. The option describing the mediastinum as between the lungs is the best fit because it directly captures the mediastinum’s location relative to the lungs themselves. The other descriptions aren’t accurate: the region between the diaphragm and lungs is not the mediastinum but part of the lower thorax near the diaphragmatic and pleural spaces; the space between the heart and lungs is not how the mediastinum is defined since the heart is itself within the mediastinum; and the pleural spaces are the lateral potential spaces around each lung, separate from the central mediastinal compartment.