Coloured 3D computed tomography (CT) of the thoracic (chest) cavity from the front. The airways (faint purple, branching left and right) are visible, as is the heart (yellow, centre) and aortic arch (yellow tube atop heart), with the ribs (yellow) seen in the background. 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) that helps distribute blood to the head and upper extremities.