What prevents the backflow of blood in the separate chambers of the heart?

Answer 1

Veins are provided with "one-way" valves along their route back to the heart. I used to notice that the veins on my forearm inflated and bulged when if I swept my fingers down from my inner-arm elbow to my wrist when I was young and skinny. This clever arrangement results in the reduction of effort on the heart to pump blood during muscular exercise.

Answer 2

Heart valves are flap-like structures that allow blood to flow in one direction. There are four valves of the heart, Aortic Valve, Mitral Valve, Pulmonary Valve, and Tricuspid Valve.