MadSci Network: Earth Sciences

Re: Why doesn't the atmosphere crush us under it's weight?

Date: Tue Mar 12 15:25:28 2002
Posted By: Renafaye Norby, Faculty, Science Education, Black Hills State Univ.
Area of science: Earth Sciences
ID: 1015787754.Es

We measure atmosphere in pressure - pounds per square inch, for a reason.
Our bodies do not support the entire weight of the atmosphere, but only the
pressure on the surface area of our body. Because our bodies have evolved
in this atmosphere, the pressure generated by our heart beating and pushing
blood through arteries and veins (which is our blood pressure) just
balances the external pressure on every square inch of our body. 

So the atmosphere pushes from the outside but our blood, pressurized,
balances that pressure as long as the "system (our circulatory system)" is
intact. If someone is cut in an artery, where the blood pressure is being
sustained by the heart, blood will spurt from that wound until the pressure
goes down due to blood loss.

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