List four functions of the human heart. Why is double circulation necessary in the human body?
Functions of the human heart-
(1) Receives deoxygenated blood from different parts of the body
(2) Sends or pump blood to lungs for oxygenation
(3) Receives oxygenated blood from the lungs.
(4) Pumps or transfer oxygenated blood to different parts of the body.
Double circulation is necessary because it does not allow the mixing of oxygenated and deoxygenated blood. This separation ensures highly efficient supply of for their energy needs.