Respiration is the process of inhaling, warming, filtering, controlling the humidity of, ad exhaling air. Lungs exchange oxygen for carbon dioxide, and the heart pumps oxygenated blood to the rest of the body. Additionally, the cilia in the lungs secrete mucus as they move back ad forth, carrying out of the lungs; dust, germs, and other matter, where it is expelled by sneezing, coughing, spitting, and swallowing.
Breathing is controlled by the diaphragm, located at the base of the rib cage. When the diaphragm contracts, it pulls down on the thoracic cavity, causing the lungs to expand and air to be inhaled. When the diaphragm relaxes, the lungs retract ad air is exhaled. The breathing process, one of the most basic and important functions performed by the body, often is taken for granted.