Atrioventricular valve:prevents backflow into atria when vents. contract tricuspid valve: 3 cusps Mitrial/bicuspid valve:2 cusps , chordae tendineae anchor the cusps to pap. muscles 1. blood gets back to heart, fills atria, av valve open, vents fill, av valve flaps hang into vents, atria contracts, forces more blood to vents, then av valves open