Your heart works to pump blood throughout your body. Without it we would die. The blood it pumps carries oxygen and nutrients to the rest of the body. It also pumps out waste. Your heart is made up of four chambers. The atria are located on both top side of your heart. The ventricles are located on the bottom of both sides. Your atria fill with blood and send it to yor ventricles. From there the ventricles pump out your blood to your lungs and the rest of your body.