Where did the organ system from the previous episode,(brain CNS, that failed us on this episode 2. Cardiac circulation starts with blood flow through small veins draining into bigger abd even bigger veins until two dump into the upper right chamber of the heart. The blood flows down through the TRICUSPID VALVE into the RIGHT VENTRICLE. The Rt Ventricle, the lower right chamber and muscle pump, pumping blood to the lungs through the PULMONIC VALVE, into the PULMONARY ARTERY as the main pulmonary artery starts, it soon branches into the RT PULMONARY ART BRANCH & LT PULMONARY ART BRANCH . The flow then branches into smaller and smaller vessels collectively called THE PULMONARY VASCULAR BED. Blood then flows through 4 PULMONARY VEINS to the LEFT ATRIUM which is the top left cardiac chamber. Blood then flows down through the MITRAL VALVE to the LEFT VENTRICLE which has a conical muscular structure that acts as a powerful pump ejecting blood up through the AORTIC VALVE and into the AORTA.