The respiratory system includes tubes that remove (filter) particles from incoming air and transport air into and out of the lungs. The system also includes many microscopic air sacs where gases are exchanged.
    The entire process of gas exchange between the atmosphere and body cells is called respiration.  Events of respiration include: (1) movement of air into and out of the lungs—commonly called breathing or ventilation; (2) gas exchange between blood and air in the lungs; (3) gas transport in blood between the lungs and body cells; and (4) gas exchange between blood and body cells. Oxygen utilization and carbon dioxide production at the cellular level is called cellular respiration.