Blood system. Artwork illustrating the blood system which supplies the body with blood. The heart (upper centre, red) is responsible for pumping the blood around the body. Here, arteries carrying oxygenated blood from the heart are shown in red, and veins carrying deoxygenated blood are blue. Deoxygenated blood goes back to the heart, where it is pumped first to the lungs (not seen) and then back around the body. Blood is pumped up to the brain (top centre, orange), and down to the other organs. The kidneys (orange, below heart) filter the blood, removing waste products. Major blood vessels also run to the arms and legs, and provide oxygen for the large muscles there.