oxygen-poor blood
Blood flows through the heart in two separate loops, which are indicated by the arrows in Figure above. You can think of them as a "left side loop" and a "right side loop. " The right side of the heart collects oxygen-poor blood from the body and pumps the blood to the lungs. In the lungs, carbon dioxide is released and oxygen obtained by the blood. The left side of the heart carries the oxygen-rich blood back from the lungs and pumps it to the rest of the body. The blood delivers oxygen to the body's cells, returning the oxygen-poor blood back to the heart.