Healthy lungs and heart. Coloured X-ray of the chest of an adult male, showing healthy lungs and heart. The two lung fields (upper left and right, green/pink) are located in the thorax. The heart occupies the space in the lower part of one lung (at centre right, yellow). The thorax is separated from the abdomen (lower centre, pink) by a thin curved diaphragm. The lungs supply the body with oxygen needed for respiration, as well as eliminating the waste product carbon dioxide. The total surface area of lung tissue exposed to the air in a healthy adult is about twice the area of a tennis court. The heart pumps blood to and from the lungs, and through the body.