Describe double circulation in human beings. Why is it necessary?

Double circulation: In human beings the blood goes through the heart twice during each cycle i.e., the blood passes through the human heart two times to supply once to the whole body. So, it is called double circulation of blood.

The double circulation of blood includes
(i) Systemic circulation and
(ii) Pulmonary circulation
(i) Systemic circulation: It supplies oxygenated blood from left auricle to left ventricle. Thereby pumped to various body parts. The deoxygenated blood is collected from the various body organs by the veins to pour into vena cavae and finally into right atrium (auricle). Right atrium transfers the blood into the right ventricle.
(ii) Pulmonary circulation: The deoxygenated blood is pushed by the right ventricle into the lungs for oxygenation. The oxygenated blood is brought back to left atrium of the human heart. From left atrium the oxygenated blood is pushed into the left ventricle. The left ventricle pumps oxygenated blood into arota for systemic circulation.

Double circulation is necessary : The right side and the left side of the human heart is useful to keep deoxygenated and oxygenated blood from mixing. This type of separation of oxygenated and deoxygenated blood ensures a highly efficient supply of oxygen to the body. This useful in case of humans which constantly energy to maintain their body temprature.


 Double circulation of blood in human heart