Healthy heart. Coloured three-dimensional (3-D) computed tomography (CT) chest scan revealing a healthy heart (green & blue, lower centre) in the ribcage (purple & yellow). Above the heart are the ascending (red) and descending (light blue) aorta, as well as the pulmonary artery (orange) and the oesophagus (tan brown, upper left). The heart is a hollow muscle which pumps deoxygenated blood to the lungs through the pulmonary artery and oxygen- rich blood to the body through the aorta. Food travels down the oesophagus to the stomach. CT scans use X-rays to form slice" images of the body, which a computer builds into a 3-D image."