Describe the function of the heart.
The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries other substances with it. The human heart is divided into four chambers. The upper two chambers are called right and left atrium and the lower two chambers are called the right and left ventricles. Right atrium receives carbon dioxide-rich blood from the body. Blood from right atrium enters the right ventricle, which contracts and pumps the blood to the lungs. On the other hand, oxygen-rich blood from the lungs returns to the left atrium. From the left atrium, blood enters left ventricle. Left ventricle contracts and pumps the blood to all parts of the body. Hence, the rhythmic contraction and expansion of various chambers of the heart maintains the transport of oxygen to all parts of the body.