The heart valves of a small child are always undergoing regular opening and closing, which is a phenomenon that occurs in order to fulfill the normal function of the heart, as discussed below. There are four valves in a child’s heart: the mitral valve between the left atrium and the left ventricle, the aortic valve between the left ventricle and the aorta, the tricuspid valve between the right atrium and the right ventricle, and the pulmonary valve between the right ventricle and the pulmonary artery. During systole, the mitral and tricuspid valves are closed, while the aortic and pulmonary valves are open, which means that during systole, the blood in the left and right ventricles is pumped into the aorta and pulmonary arteries. During diastole, the aortic and pulmonary valves are closed, while the mitral and tricuspid valves are open, which means that during this period, the left and right ventricles will pump blood from the left and right atria.