As the heart beats, it pumps blood through a system of ... (Photo Credit: iStock/Getty Images) The atria and ventricles work together, contracting and relaxing to pump blood out of the heart.

(Photo Credit: iStock/Getty Images) Your pericardium is a tough, double-layered sac. It keeps your heart in a stable place in your chest as your heart beats. In healthy people, the pericardium ...