Blood pressure and atmospheric pressure

In summary: Thank you for your reply. I was not sure if you meant that the blood pressure is not noticeably compressed at all or if the pressure difference is not large enough to cause any significant damage. I think it is the latter. Although the pressure difference is not large, it is still enough to cause damage if it is not maintained.
  • #1
ananthu
106
1
The normal atmospheric pressure is 760 mm of Hg. But the normal human blood pressure is around 120/80 mm only. In that case how equilibrium of our body is achieved? For any vessel to retain its original shape its inside pressure and outside pressure should remain equal. If the outside pressure exceeds the vessel will be crushed inward and if the inside one exceeds it will blow up. In the case of our body, assuming it as vessel, how the pressure of atmosphere which is nearly six times higher than the blood pressure inside, could not crush the body inward?
Are there any other inward forces make up for the rest in order to counteract the atmospheric pressure? Also why do we not feel the atmospheric pressure acting on our body surface at all?
 
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  • #2
The blood pressure measurments are "relative pressure", meaning the figures that you state are above atmospheric pressure.
 
  • #3
Thank you for your reply. But I couldn't follow what you exactly mean. Will you please elaborate?
 
  • #4
760+120=880

Think about it: the measurement is taken with a pressure measuring device open to atmosphere.
 
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  • #5
Does it mean that the actual blood pressure is 880 mm of Hg? In that case it means the actual blood pressure is 120 mm higher than that of the outside pressure.If so how balance is achieved? If there is no balancing mechanism, I should feel as if my blood is pushing my body from inside!
 
  • #6
Mechanical strength of blood vessels.

Not everything gets crushed because of a pressure difference. Think of, a can of fizzy drink, a high pressure hose pipe, gas/water pipes, an aeroplane. All are pressure containers.

So just like a waterpipe with high pressure water rushing through it doesn't explode (usually) neither do blood vessels. Note that if blood pressure get's too high, your blood vessels can break.
 
  • #7
120 mm is not a lot of pressure for a hose like your blood vessels to hold.
 
  • #8
russ_watters said:
120 mm is not a lot of pressure for a hose like your blood vessels to hold.

That may seem true, but recall that hypertension starts around 140 mmHg: that's an increase of only 2% absolute pressure. (16% increase in gauge pressure, tho).
 
  • #9
Thank you for all the replies. I am happy that my doubts and the chain of answers have led to a new realm of interesting details and facts which are seldom found in textbooks.
 
  • #10
ok, i guess its really2 fair explanation. but, if thts the case, when 1 person die, we must observe tht the body would shrink with 880 mmHg pressure. 880 is a huge pressure difference. if the difference is maintain to 120-80, meaning, our heart is just the elevation (pumpung power of only 120)...dont u guys think so?

I still damn impressed with the design of the heart to sustain pumping on average of 100000 times a day even with that 120 pressure ramp.
 
  • #11
Welcome to PF!

Pressurized and compressed are two different things. Our blood is pressurized, but is not noticeably compressed.
 
  • #12
ok, get the point. (correct me if its not allign with what u try to explain)..basically, after someone die, there is no more pressure generated from inside, that would definitely damage the body as pressure inside is not in equilibrium with pressure outside. however, due to the physical properties of human body which built from very minimal compressible substances, so tht, our body could still maintain its original state even without internal pressure generated from the blood circulation.is tht the point?
 
  • #13
From my understanding a pressure gradient is required for gas to exchange from one system to the next, such as from the atmosphere into our blood. The atmospheric pressure is not that high if you compare it to our circulatory pressure - atmospheric pressure is 14.69psi and our systolic blood pressure is 2.32psi. Our blood vessels are composed of soft and hard tissues that enable our circulatory system to with stand a certain amount of pressure from outside as well as from within. 14.69psi is a small amount of pressure - enough for gaceous exchange but not enough to crush a human body or a blood vessel. Consider that Oxygen has partial pressure of 0.21atm (160mmHg), which is necessary for Oxygen to enter the blood as our systolic blood pressure should be about 120mmHg. The atmospheric pressure of CO2 is less than 0.0397atm (30mmHg), which is also necessary for the CO2 to diffuse out of our blood and into the atmosphere. A fine balance indeed.
 

FAQ: Blood pressure and atmospheric pressure

What is blood pressure?

Blood pressure is the force that blood exerts against the walls of your blood vessels. It is measured in millimeters of mercury (mmHg) and consists of two numbers, the systolic pressure (top number) and the diastolic pressure (bottom number).

What factors affect blood pressure?

Several factors can affect blood pressure, including age, genetics, diet, physical activity, and stress levels. Certain health conditions such as obesity, high cholesterol, and diabetes can also impact blood pressure.

How does atmospheric pressure affect blood pressure?

Atmospheric pressure is the pressure exerted by the weight of the atmosphere on the Earth's surface. Changes in atmospheric pressure can affect blood pressure due to the body's natural response to maintain balance. For example, when atmospheric pressure decreases, blood vessels may dilate to compensate, causing a decrease in blood pressure.

Can changes in atmospheric pressure cause health problems?

In healthy individuals, small changes in atmospheric pressure are unlikely to cause any health problems. However, individuals with pre-existing conditions such as heart disease, lung disease, or migraines may experience symptoms such as chest pain, shortness of breath, or headaches during significant changes in atmospheric pressure.

How can I manage my blood pressure?

The best way to manage blood pressure is by maintaining a healthy lifestyle. This includes regular exercise, a balanced diet, maintaining a healthy weight, limiting alcohol and tobacco use, and managing stress levels. It is also essential to regularly monitor your blood pressure and consult with your doctor if it consistently falls outside of the healthy range.

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