1 The chest cavity, or thorax (pronounced: thor-aks), is the airtight box that houses the bronchial tree, lungs, heart, and other structures. 2  Whenever we humans exhale, a certain quantity of air remains in the lungs, the bronchial tree, and the trachea-since those structures cannot completely collapse, as a balloon can.xample sentences. 1  Endoscopy has made it possible to obtain specimens from stomach or colon, or from the bronchial tree in the lungs, which can be examined by histological techniques, allowing an accurate diagnosis to be made.