The respiratory tract is the set of structures responsible for the intake of air for it's oxygen and the exhalation of air containing higher concentrations of carbon dioxide. It consists of: * The upper respiratory tract (nose, nasal passages, nasal sinuses and throat * The respiratory airways (larynx, trachea, bronchi and bronchioles * The lungs (respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli)