The human heart is divided into four chambers where the upper two chambers are called right and left atrium and the lower chambers are called the right and left ventricles, therefore the functions of the heart are as follows:
(i) The right atrium receives carbon dioxide-rich blood from the body. Blood from the right atrium enters the right ventricle, which contracts and pumps the blood to the lungs.
(iii) Oxygen-rich blood from the lungs returns to the left atrium, then blood enters the left ventricle which contracts and pumps the blood to all parts of the body.
Hence basic function is to beat with rhythmic contraction and expansion throughout the life and transport the blood as a pump.