Final answer:
The statement is false; the lungs are enclosed in their own pleural cavities, which are on either side of the mediastinum, not inside it. The mediastinum contains the heart but not the lungs.
Step-by-step explanation:
The statement that the lungs and heart are contained within the mediastinum, which separates the thoracic cavity into the left and right pleural cavities, is False. The mediastinum contains the heart along with other structures such as the trachea, esophagus, and major vessels, but the lungs are not within the mediastinum.
Instead, each lung is enclosed in its own pleural cavity, and these cavities are on either side of the mediastinum. The thoracic cavity is divided into three principal subdivisions: the medial mediastinum containing the heart, pericardial cavity, trachea, esophagus, and associated structures, and the bilateral pleural cavities, each encompassing a lung.
The pleural cavity is the potential space between the visceral and parietal pleurae, and it is these pleurae that enclose and protect the lungs. The diaphragm forms the lower boundary of the thoracic cavity and separates it from the abdominopelvic cavity.