Question
How do gases cross the respiratory membrane?
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Answer
By passive diffusion down partial-pressure gradients; no ATP used.
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Question
Hydrostatic pressure
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Answer
Pressure from fluid depth: Pgauge=ρgh; depends only on vertical depth.
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Question
What determines alveolar gas composition in the lungs?
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Answer
Dalton's law plus humidification and residual CO2 set alveolar partial pressures.
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Question
Why are arterioles the main regulators of vascular resistance?
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Answer
Flow and resistance depend on r4, so small radius changes have huge effects.
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