The process of breathing is generally referred to as respiration. It involves the inhalation of atmospheric oxygen and the exhalation of carbon dioxide, which is a metabolic waste product.
The breathing process is facilitated by the respiratory system, which is primarily composed of the lungs, diaphragm, trachea and bronchi. Inhalation, also known as inspiration, starts by taking in oxygen-rich air through the nose and mouth. The air travels down the back of the throat and then into the trachea where impurities are removed.
Oxygen from the air then enters the lungs through the bronchial tubes that branch out of the trachea. The exchange of oxygen and carbon dioxide occurs in the lungs, where the oxygen is absorbed by the red blood cells and circulated throughout the body. Carbon dioxide is expelled from the lungs through exhalation, also referred to as expiration.