Question

describe double circulation in human beings schematically why is it necessary

Answer 1

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.

Answer 2

double circulation has two components- pulmonary circulation and systematic circulation.

pulmonary circulation is movement of blood from heart to the lungs and back from lungs to the heart.
deoxygenated blood of the body enters the right auricle passes into right ventricle which pumps it into the permanary arch, to separate pulmonary arteries the blood passes into the lungs
now oxygenated blood from the lungs is carried back to the heart by pulmonary veins and enters into the left Atrium or auricle of the heart .
systematic circulation is the circulation of blood between heart and different part of the body accept lungs. oxygenated blood received by the left auricle passes into left ventricle . the left ventricle pumps into aorta for supply two different body parts including walls of the heart with the help of arteries