The job of your heart is to pump blood through your body. Even in your sleep, your heart keeps beating, or pumping blood. If it stopped, you would quickly die. Your heart is broken into two sides, separated by a septum. The Left side of your heart is filled with oxygen rich blood, while the right side of your heart is filled with oxygen poor blood. Each side of your heart is further broken into two chambers, known as the atrium, and the ventricle. Each side of the heart has an atrium and a ventricle for a total of four chambers.