Coloured 3D computed tomography (CT) angiogram scan of a healthy heart and the blood vessels that carry blood to and from the heart. The heart is a hollow sac of muscular tissue that pumps oxygenated blood around the body and deoxygenated blood to the lungs. At lower centre is the aorta, the body's main artery, which distributes oxygenated blood from the heart-lung system to the rest of the body. The airways (pink) of the lungs are seen either side of the heart.