The role of blood is to carry nutrients and oxygen to our organs and our brain.
For a short answer, blood is sort of like a fuel, like gas to a car. If blood is not pumping through your system than you will die just like if gas is not pumping through a car's engine, it will break down.
Your body makes more blood everyday.
It makes blood cells.
Bones
It makes blood cells.
Blood makes up 7% of the weight of the body in humans. See: http://en.wikipedia.org/wiki/Blood
The human body makes its own blood, it is impossible to synthesize.
You heart pumps the blood round
Red blood cells are manufactured in the bone marrow.
Heart.
the heart pumps the blood to different part of the body
That makes no sense!
the heart beating the blood around the body