Coloured 3D computed tomography (CT) scan of a heart and blood vessels, including the aortic arch (curved tube on top of heart) and the pulmonary blood vessels that carry blood to and from lungs. The heart is a hollow sac of muscular tissue that pumps oxygenated blood around the body and deoxygenated blood to the lungs. The aortic arch is the segment of the aorta, the bodys main artery (also seen descending below the heart), that helps distribute blood to the head and upper extremities.