i understand what you are describing with your analogy but i don't understand how to look at it in terms of physio.
so let me be more specific with my question
1. As we breathe, does the pleural pressure remain constant or does it change?
2. I don't understand how alveolar pressure changes. Shouldn't it be more or less constant since gases exchange via diffusion, not really changing their concentration? Specifically total pressure stays the same. Partial pressures of the gases changes though for sure.. But the answer doesn't indicate this. Just says pressure.