Coloured 3D computed tomography (CT) angiogram scan of the aorta (red, top centre to right), the pulmonary artery (red, upper right) and the vena cava (red, centre) as they leave and enter the heart. The aorta is the body's main artery, distributing oxygenated blood from the heart-lung system to the rest of the body. The pulmonary artery carries deoxygenated blood from the heart to the lungs. The vena cava returns deoxygenated blood from the body to the heart. The white branching structures at right and left are the bronchioles (airways) of the lungs.