The mediastinum is the cartilage that forms the lower portion of the breast bone.

a. true

b. false

The answer is False. The mediastinum is not a cartilage that forms the lower portion of the breast bone, the mediastinum is the middle part of the chest cavity, which is located between the lungs of an individual. The Mediastinum is the area located between the lungs, it contains organs such as the heart and its large arteries and veins. It may also include the trachea, the esophagus, the bronchi and last but not the least the lymph nodes.