How the heart works?
the heart has two pumps. each pump has two chambers , the upper and lower chambers . the upper chambers is the atrium that receives blood coming in from the veins . the lower chamber is the ventricle that forces the blood out into the arteries . there is a valve between each atrium and ventricle to prevent the blood from flowing backwards . the valves are like one-way doors that keep the blood moving in only one direction . valves Control movement of blood into the heart chambers and out to the aorta and the pulmonary artery .