CBSE Class 7 Answered

As the ventricles of the heart contract, they push blood into the small lumen of the arteries with a great force, thus making the blood in the arteries flow in spurts and under pressure. 

Blood in human body undergoes double circulation.

Double circulation is a circulation in which the blood, before going to the general circulation rounds the body, enters the heart twice, first as deoxygenated blood and then as oxygenated blood. The oxygenated blood goes to the general circulation.