De-oxygenated blood flows through superior/inferior vena cava into the right atrium, through the tricuspid valve, to the right ventricle, through the pulmonary valve, into the pulmonary arteries, to the right/left lungs and becomes oxygenated, into the pulmonary veins, into left atrium, through the bicuspid/mitral valve, into left ventricle, through the aortic semilunar valve, into Aorta, into the upper and lower body, de-oxygenated blood flows through superior/inferior vena cava, process repeats