Breathing. Coloured X-ray showing inhalation (left) and exhalation (right). The horizontal bands are the ribs, enclosing the lungs (dark blue). The heart is brown mass at lower right, while the diaphragm (brown) runs along the bottom. During inhalation the ribs move up and to the side, and the diaphragm contracts, moving down, allowing the lungs to expand and fill with air. During exhalation the opposite happens, the ribs moving down and in, and the diaphragm relaxing and moving up. This forces air out of the lungs, and also pushes the heart upwards.