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I have been studying the abdominal cavity and trying to draw analogies between what I learned in chemistry with ideal gasses and the abdominal cavity. However, the abdominal muscles and fascia are not rigid surfaces and therefore, as a container it is deformable.

How do I describe the deformations that occur to a container containing an ideal gas if the initial conditions are changed? (E.g. higher pressure)

Stan Shunpike
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  • If the container can deform it just means that V can change. – valerio Jul 26 '17 at 00:07
  • Ok, what I want to know then is, how do you model the stretching of the surface as the properties of the gas (e.g. Temperature changes? – Stan Shunpike Jul 26 '17 at 00:25
  • PV=nRT provides the equation-of-state of an ideal gas. It provides full information on how the gas will respond to variations in pressure, volume, and temperature. It has all the physics that you need about how the gas will behave for your deformable container problem. You just need mathematically describe the appropriate constraints and apply them to the equation. –  Jul 26 '17 at 00:25
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    It's a thermodynamic problem involving the tensile energy of the cavity. – dmckee --- ex-moderator kitten Jul 26 '17 at 00:46
  • Rephrasing the intent of dmckee's comment, he's saying you need additional equation(s). The ideal gas law alone is not sufficient to describe your total system. These equations are not necessarily simple since muscle tension can change by will of neuromuscular action. Unless you are dealing with a sedated patient. Then you might be able to use just a simple model. But probably nonlinear. – docscience Jul 26 '17 at 01:25
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    As a first step you might want to model a simple elastic balloon then validate your model by experiment. I expect you'll find issues even with this simpler model/system. – docscience Jul 26 '17 at 01:27
  • Yeah, i was thinking of just considering an elastic kind of system, like a balloon – Stan Shunpike Jul 26 '17 at 01:51
  • It is more like a bag with the external pressure changing due to the contraction/relaxation of the intercostal muscles and the muscles associated with the diaphragm and this produces an increase and decrease in the volume of the bag. – Farcher Jul 26 '17 at 08:46
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    see Why is filling a balloon from your mouth much harder initially? – sammy gerbil Jul 26 '17 at 13:10

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