So remember, the atrium always accepts the blood into our heart. Now, the blue arrow basically designates the movement of deoxygenated blood. But the red arrow designates the movement of oxygenated blood blood that contains our red blood cells with the oxygen. Now, from our right atrium, our blood flows through this valve system and into the right ventricle. So number two, it then enters the right ventricle. And this is essentially where the systemic circulation ends and the pulmonary circulation begins.