The respiratory system is responsible for taking in oxygen and removing carbon dioxide from the body. It consists of the lungs, airways (nose, trachea, bronchi), and diaphragm. Air is inhaled through the nose or mouth, travels down the trachea, and enters the lungs where oxygen is exchanged for carbon dioxide in tiny air sacs called alveoli. The diaphragm helps with breathing by contracting and relaxing to move air in and out of the lungs.