Before blood can begin its journey around the body again, it must travel to the lungs to release carbon dioxide and take in oxygen. The right atrium accepts the oxygen-poor blood and delivers it to the right ventricle, which pushes the blood through an artery to the lungs. The blood then returns in a vein from the lungs to the left atrium, where it waits before passing to the left ventricle and back through the aorta again.
While your blood is traveling through your body, it undergoes another important process: waste filtration. When blood leaves the body's tissues to travel back to the heart and lungs, it carries excess nutrients and other items that your body cannot use.