This medical video demonstrates blood circulation whose purpose is to bring oxygen-bearing blood to all the tissues of the body. When the heart contracts it pushes the blood out into two major loops or cycles. In the pulmonary loop, the blood circulates to and from the lungs, to release the carbon dioxide and pick up new oxygen. The systemic cycle is controlled by the left side of the heart, the pulmonary cycle by the right side of the heart. Let’s look at what happens during each cycle. In the systemic loop, the blood circulates into the body’s systems, bringing oxygen to all its organs, structures and tissues and collecting carbon dioxide waste.