Anatomy and Physiology of Lower Respiratory system: The lower respiratory system, or lower respiratory tract, consists of the trachea, the bronchi and bronchioles, and the alveoli, which make up the lungs. These structures pull in air from the upper respiratory system, absorb the oxygen, and release carbon dioxide in exchange. Other structures, namely the thoracic cage (or rib cage) and the diaphragm, protect and support these functions (Man, 2017).