Where are the heart and great vessels located?

• A. Behind the lungs in the posterior thorax
• B. Between the lungs in the middle third of the thoracic cage (mediastinum)
• C. In the left lung only
• D. At the rear of the diaphragm

Answer: (B)

The main idea here is that the heart and its major vessels reside in the mediastinum, the central compartment of the chest. This space sits between the two lungs, within the middle third of the thoracic cage. The heart sits in a protective sac (the pericardium) there, with the great vessels forming the central connections to the rest of the circulation. Because the lungs fill the sides of the chest, the heart is positioned between them rather than inside one lung, so describing them as between the lungs in the middle portion of the thoracic cavity—i.e., in the mediastinum—is the most accurate statement.