Coloured 3D computed scan (CT) angiography scan of a healthy heart, aorta (purple) and pulmonary arteries. The heart is a hollow sac of muscular tissue that pumps blood around the body. The aorta (purple upper centre) carries blood to the body. To the left of the aorta is the upper part of the vena cava vein (blue). This vein carries deoxygenated blood into the heart from the body. This blood then travels from the heart to the lungs (where it obtains oxygen) and back to the heart through the pulmonary artery (green).