Route of blood flow through the heart?

Blood flows into the right atrium from the systemic circulation, which returns blood from all the tissues of the body. Blood then flows into the right ventricle, which completes filling as the right atrium contracts. Contraction of the right ventricle pushes blood against the tricuspid valve, which closes, and the pulmonary semilunar valve, which opens, allowing blood to enter the right atrium. The pulmonary artery carry blood to the lungs, where carbon dioxide is released, and oxygen is picked up. Blood returning from the lungs enters the pulmonary vein through the four pulmonary trunk. Blood passing from the left atrium to the left ventricle opens the bicuspid valve, and contracton of the left atrium completes filling of the left ventricle. Contraction of the left ventricle opens the aortic semilunar valve allowing blood to enter the aorta.