What forces the blood to flow?? I'm confused...

the heart pumps d blood to d otha parts of d body. wen pumpin it exerts pressure on2 d arteries. tt forces d blood 2 flow. d concentration gradient of oxygen and carbon dioxide does not affect the blood flow much. n, dere r only 4 valves in d heart tt help in d process of pumpin blood 4 circulation 2 n fro in d body.