Why doesn't our body experience equal pressure when we press our finger?

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Discussion Overview

The discussion centers around the application of Pascal's Law to the human body, specifically questioning why equal pressure is not experienced throughout the body when pressing a finger, given that the body contains fluids such as blood and water. The scope includes theoretical considerations of fluid dynamics and biological structures.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that according to Pascal's Law, pressure should be equal throughout a confined fluid, questioning why this does not apply to the human body.
  • Others argue that the human body does not behave as a perfect fluid due to factors such as skin elasticity, the presence of air in the lungs, and the active role of the heart and arteries in creating pressure differentials.
  • One participant notes that modeling the body as a simple bag of fluid is inaccurate, as bones and organs behave more like solids than liquids.
  • Another participant suggests a model of the body as a balloon filled with water, indicating that pressure changes would occur throughout the model, yet acknowledges the complexity of applying basic physics to biological structures.
  • Some participants express confusion about the relevance of the fluid content in the body, questioning the implications of having fluids like blood and hormones in this context.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus, as there are multiple competing views regarding the application of Pascal's Law to the human body and the complexities involved in modeling biological systems.

Contextual Notes

Limitations include the oversimplification of biological structures when applying fluid dynamics principles, as well as the variability in how different tissues respond to pressure changes.

aditya ver.2.0
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According to Pascal Law, when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container. Then why doesn't our entire body experiences the same pressure throughout the body when we press our finger. Isn't the entire body filled with fluid, i.e. blood and water?
 
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aditya ver.2.0 said:
According to Pascal Law, when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container. Then why doesn't our entire body experiences the same pressure throughout the body when we press our finger. Isn't the entire body filled with fluid, i.e. blood and water?

Our bodies don't behave as perfect fluids. They're covered with skin that stretches differently in different directions, the lungs are full of air which obeys Boyle's law instead of Pascal's, the heart and arteries are working hard at creating pressure differentials throughout the circulatory system, membranes in the kidneys and digestive track do interesting things with osmotic pressures, bones, tendons, and connective tissues are fairly solid...

Modeling the human body as a bag filled with liquid isn't very accurate across a wide range of conditions, including (not coincidentally) those which we most often encounter in daily life.
 
But sir, still our body has a large portion of fluid ranging from blood to hormones. So what the problems?
 
The problem is, the human body is still not a bag of skin with a bunch of fluid inside. When you move your body, you don't slosh inside, like when you carry a pail half-filled with water. Your bones, organs, muscles, etc. behave closer to solid materials than they do liquids.
 
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aditya ver.2.0 said:
But sir, still our body has a large portion of fluid ranging from blood to hormones. So what the problems?

You could model the body as a sausage shaped balloon, full of water (it would need to be contained in some sort of basket or it would form a tear drop shape ). In that model, if you squeezed the top, the pressure at the bottom would also increase.

It is usually very problematical to try to apply simple basic ideas in Physics to complicated biological structures. There are too many variables involved for an accurate answer to be obtained.
 

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