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Lungs and heart. Historical illustration of the heart-lung system. At top (front view), the heart (brown, upper centre) receives deoxygenated blood from the superior vena cava vein (blue, upper left of heart). The blood is pumped via the pulmonary artery (blue, upper right of heart) to the lungs (large structures, upper right and left). The blood is oxygenated in the lungs and returned to the heart via the pulmonary veins (red). It is then pumped into the aorta (orange) and around the body. At bottom (rear view), the trachea (yellow and white stripes) supplies air to the lungs. Colour lithograph by Fairland from The Viscera of the Human Body, 1840. Based on drawings by Bagg. (KEYSTONE/SCIENCE PHOTO LIBRARY/SHEILA TERRY)