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