Atmospherical pressure is around 760 mmHg, while blood pressure is on average 100 mmHg. Then why do you bleed from cuts, and why does a cut aorta spray blood? The atmosphere should press the blood back in, or at least stop it from spraying.
Because liquids and gases exerts same pressure and the density of liquids is more than gases. So,blood is also a liquid that is why blood flow when we get cut .