What is The Causes that make Intrapleural pressure is negative ??

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Askar

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Hello ,,

Sorry for my language

First :
1 - We know That Intrapleural Pressure = 756 ( subatmosphare )
2 - and intraAlveoli Pressure = 760

That mean Streched Lung Beacuse there are Pressure Gradeint between (Intrapleural Pr and Intrapleural Pr )

Second :
1 - Intrapleural Pressure = 756 ( substmosphare )
2 - atmosphare Pressure = 760

That Mean Chest wall is compressed


My Quastion :
1 - How intrapleural Pressure Become Negatively ??????

Note : in my book written ( That factors make intrapleural Pressure Negatively is ( 1 - Alveoli recoil + Chest to become uncompressed ))

but iam not understanding and i cant combined The idea

please help me 🙁
 
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Think of the intrapleural cavity as a suction device. Even when you are resting, your lungs want to shrink a lot and your chest wants to expand. The intrapleural cavity "glues" them both together by being at a low pressure.

As for how the pressure lessens during inspiration, if I remember correctly it is because your chest is not as elastic as your lungs. So as your chest is expanding, your lungs are really getting stretched out and pulling back on the intraplerual cavity. I don't remember exactly, but I think this causes little pockets of air to form in the intrapleural cavity, thus lowering the pressure. An easier way to think about it is imagine if the intrapleural cavity is filled with gas, as it stretches out, the volume expands and pressure lessens.
 
Intrapleural pressure is negative relative to atmospheric pressure.

When the diaphragm external intercoastal muscles contract, the chest cavity expands - volume increases and pressures decreases relative to atmospheric pressure and air moves into the lungs -> inspiration

due to the recoil abilities of the lungs, chest cavity volume decreases, pressures increases relative to atmpospheric pressure and air moves out of the lungs, into the atmosphere -> expiration
 
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