Final answer:
The lungs are not located within the mediastinum; they are housed in the pleural cavities on either side of it. Other structures like the heart, thymus, and esophagus are indeed found within the mediastinum.
Step-by-step explanation:
The structure not located within the mediastinum is the lungs. The mediastinum is the central compartment of the thoracic cavity, which houses structures such as the esophagus, heart, thymus, and other important vessels and tissues but not the lungs. The lungs are located on either side of the mediastinum within the pleural cavities. The heart, specifically, is positioned within the pericardial cavity of the mediastinum, and the thymus sits in the space between the sternum and the aorta of the heart. Additionally, the esophagus runs through the mediastinum behind the trachea, heart, and lungs and penetrates the diaphragm at the esophageal hiatus to enter the abdomen.
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