This has been driving me crazy. I know the general mechanism of breathing - diaphragm contracts, causing more volume in the lungs, so air rushes in. What I don't understand is how this is related to intrapleural pressure and alveolar pressure. Someone please help!
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ok, I'm just gonna stick to the intrapleural pressure, because I'm kind of lazy.
Anyway, your diaphragm contracts, and the pressure becomes more negative, letting the alveolar sacs inflate, and blah blah blah. I can see that you already know this.
Anyway, what would happen if the lungs were to completely deflate?
da da da da da da (jeopardy music).
You got it! they will collapse. and a collapsed lung always needs outside help to reinflate. You see, the intrapleural cavity has a constant negative pressure. This allows the outside pressure (alveolar pressure) to exert force and maintain proper background inflation of the lungs to prevent complete collapse.
If the intrapleural pressure equaled the alveolar pressure, then there would be nothing to keep the lungs from collapsing completely on exhale. That pretty much sums it up. This is why people get "collapsed lungs" when they are stabbed through the pleural membrane. The intrapleural cavity pressure becomes equal to ambient atmospheric pressure, and well you see where this is going.
I also realized i answered a little about intrapleural AND alveolar pressure.... so much for being lazy, huh?
Anyway, your diaphragm contracts, and the pressure becomes more negative, letting the alveolar sacs inflate, and blah blah blah. I can see that you already know this.
Anyway, what would happen if the lungs were to completely deflate?
da da da da da da (jeopardy music).
You got it! they will collapse. and a collapsed lung always needs outside help to reinflate. You see, the intrapleural cavity has a constant negative pressure. This allows the outside pressure (alveolar pressure) to exert force and maintain proper background inflation of the lungs to prevent complete collapse.
If the intrapleural pressure equaled the alveolar pressure, then there would be nothing to keep the lungs from collapsing completely on exhale. That pretty much sums it up. This is why people get "collapsed lungs" when they are stabbed through the pleural membrane. The intrapleural cavity pressure becomes equal to ambient atmospheric pressure, and well you see where this is going.
I also realized i answered a little about intrapleural AND alveolar pressure.... so much for being lazy, huh?
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The lungs are covered by a thin membrane of epithelium, known as the pleural membrane. The key to understanding how gas exchange works is this pleural membrane. The space inside the membrane, which contains the lungs, is called the pleural cavity. The pressure inside the pleural cavity is LOWER than atmospheric pressure. This ensures air enters the lungs. Remember, gas always flows from an area where it is under greater pressure to one where it is under lower pressure. If the air pressure in the pleural cavity became greater than the air pressure in the atmosphere, your lungs would collapse.
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