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Related Flashcards
Cards In This Set
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Movement of gas into the alveolus is by _______
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Bulk flow (down the airways)
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Movement of gas out of the lung is by ______
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Bulk flow (in the blood vessels)
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What happens to gas movement as you move down the tracheobronchial tree?
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It slows down with the increasing cross-sectional area so that by the time you reach the opening of the alveolus, the bulk flow has stopped. There, transfer of gas is by diffusion based on random movement of molecules down their concentration gradients.
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What is diffusion?
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The net transfer of gas molecules down a concentration gradient by random movement.Note: there is movement of gas in both directions, but the overall net transfer is DOWN the concentration gradient.
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Where does gas diffusion occur?
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It occurs in the gas phase at the alveolar membrane.It also occurs across the alveolar membrane, with CO2 moving into the alveolus from the blood and O2 moving out of the alveolus into the blood.
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Diffusion of gas in the liquid phase is affected by its _________. How?
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Solubility. Higher solubility --> faster/easier the gas will diffuse into the liquid phase. Lower solubility --> slower/less gas will diffuse into the liquid phase.Having lower solubility means that more gas molecules are likely to leave the liquid phase and re-enter the gas phase.
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Henry's Law
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The amount of gas absorbed by a liquid with which it does not combine chemically is directly proportional to the partial pressure and solubility of the gas in the liquid.
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T/F. The partial pressure of a gas in the gas phase that is the same as the partial pressure of the gas in the liquid phase means that the same number of gas molecules is present in both the gas and liquid.
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FALSE. The PO2 of gas in the air can be the same as the PO2 in the liquid, but the number of O2 molecules in the air is much higher than the number of O2 molecules in a body of water. If this were not true, then we wouldn't have a need for Hemoglobin to bind the oxygen in the liquid phase.
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Why do we need hemoglobin?
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To bind O2 in the liquid phase to keep more O2 in the liquid phase. O2 has a low solubility in water, so it is more likely to escape into the gas phase. So we have Hb to bind to it and keep it in the liquid phase.
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What is the key thing to remember about gas partial pressure in a liquid?
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It reflects the tendency of the gas to leave the liquid phase and re-enter the gas phase
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Amount of gas in a liquid is related to what 2 key factors?
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1) Solubility of the gas in that liquid2) Partial pressure of the gas
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Fick's Law
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Diffusion rate is directly proportional to the area (A) and pressure difference (P1 - P2), and inversely proportional to the diffusion distance or thickness (T)diffusion rate = D x [(P1 - P2)A/T]
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Diffusion constant, D
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Unique for a gas; it is directly proportional to the solubility of that gas and inversely proportional to the square root of the molecular weight of the gas
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T/F. If the gas is diffusing into another gas phase, solubility does not matter.
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True. Solubility only matters when the gas is diffusing into a liquid phase.
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Pressure gradient for CO2 from blood to alveolus
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PCO2 in blood = 45 mmHgPCO2 in alveolus = 40 mmHg
5 mmHg pressure gradient |
