Human heart is just like a pump of our body. It has four chambers – the 2 atria i.e the right atrium and the left atrium and 2 ventricles i.e. the right ventricle and left ventricle. First thr right atrium receives the impure blood from our body, and transfers it to right ventricle. The right ventricle pumps this impure blood to our lungs where this blood gets purified. The left atrium then receives this pure blood from the lungs and transfers it to left ventricle. The left ventricle then pumps this pure and fresh blood to our body by blood vessels.