Describe double circulation in human beings. Why is it necessary?
The heart of human beings consist of two sides right and left. The right side of the heart receives de-oxygenated blood from the cells and tissues and sends it further for purification to lungs. The left side of the heart receives oxygenated blood from lungs which is pumped further and sent to all the parts of the body through blood vessels. This is called double circulation. The energy demand of human beings is too large and hence it is necessary for the separation of oxygenated and deoxygenated blood to meet this energy demand.
