Explain blood flow through the heart

Superior and inferior vena cava enters the right atrium which is pumped by the tricuspid valve to the right ventricle and to the pulmonary valve to the pulmonary artery then to the lungs from the lungs back thru the pulmonary veins entering the left atrium pumped by the mitral valve to the left ventricle to the aortic valve to the aorta.  

The circulatory system is important in meeting the needs of all cells in the body because it offers means of transport by which cells obtain the materials needed to live and function.