The respiratory system supplies the body with oxygen, which provides energy to the cells. Another important function of the respiratory system is to remove carbon dioxide from the blood stream.
The airways, lungs and respiratory muscles form the respiratory system. The airways include the mouth, nose and trachea. These are where air and oxygen enter the body. Oxygen enters the lungs via the bronchi, which splits from the trachea. The bronchi divide again, forming bronchial tubes. Bronchial tubes split into smaller tubes called alveoli. The alveoli allow oxygen to enter the blood supply and carbon dioxide to exit it. The diaphragm muscle supports inhalation and exhalation of air from the lungs.