The Double Circulatory System
Humans have a double circulatory syatem- two circuits joined together. The first one pumps deoxygenated blood to the lungs to take in oxygen. the blood then returns to the heart. The second one pumps oxygenated blood around the body. The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again.