Question

describe double circulation in human being？

Answer 1

Human beings have completely partitioned 4 chambered heart that do not allow the mixing of oxygenated and deoxygenated blood in the ventricles.....
In double circulation, the blood from the right ventricle is pumped to the lungs through pulmonary artery (only artery carrying deoxygenated blood) ,this circulation is called pulmonary circulation......
Whereas the left ventricle pumps blood to all the parts of the body through aorta ,this circulation is called Systemic circulation.

NOTE : Walls of left ventricle is thicker than the walls of the right ventricle due to the above reason........

Answer 2

During a single cycle blood goes twice in the heart which is known as double circulation. It is necessary in human being to separate oxygenated and de-oxygenated blood because this makes their circulatory system is more efficient and helps in maintaining constant body temperature.