The mediastinum contains all of the following except:

The mediastinum is an anatomical area located in the thoracic cavity, situated between the two lungs. It contains various critical structures, including the heart, esophagus, trachea, and major blood vessels like the aorta and superior vena cava.

The lungs, however, are not classified as part of the mediastinum. Instead, they occupy the lateral portions of the thoracic cavity, with the mediastinum lying centrally between them. This clear division emphasizes the lungs' function as the organs for respiration, contrasting with the mediastinum's role as a conduit for vital structures essential for circulatory and digestive functions.

Understanding the anatomical relationships in the thoracic cavity is crucial for proper coding, anatomy studies, and treatment planning, as it helps delineate the boundaries and positions of various organs and structures.