Breathing is controlled by your body’s pulmonary system, which is made up of the system of organs used for respiration. The three main elements of the pulmonary system are the diaphragm, the lungs and the airways. The respiration process has two key stages:
1. Pumping air into the lungs. The diaphragm, a large horizontal muscle below the ribcage, generates a pumping action that moves air in and out of the lungs through a system of pipes, or airways, including the nose and mouth.
2. Gas exchange. Inside the lungs, gas exchange takes place. The pulmonary system is responsible for oxygenating the blood, and removing carbon dioxide and other gaseous waste from the bloodstream. Efficiently removing alkaline carbon dioxide from the bloodstream also helps the body to maintain its level of acidity. This process happens inside the lungs when the circulating blood is brought to the lungs’ surface through tiny blood capillaries lining each lung. The lungs need a large surface area for the diffusion of gases, and the inner surface of the lungs is moist and thin enough to allow gases to pass through.
Your lungs are very soft and pliable organs, and when they are full of air they expand to fill all the space in your ribcage. In one day, your lungs will expand and contract approximately 20 000 times. If you breathe in polluted air, your body can protect itself by breathing the pollutants out again, or by swallowing them so they’re passed out through the intestines or destroyed by digestive juices. If pollutants get as far as the bloodstream, they can be eaten by macrophages, a form of white blood cell designed to destroy infections and foreign bodies.