During respiration, oxygen is inhaled through the airways into the alveoli where gas exchange occurs. For each condition described below, state if the flux of oxygen through the blood gas barrier into the pulmonary capillaries increases or decreases. Use Fick’s law to justify your answer. a. Climbing to the top of Mt. Everest b. More abundant but smaller alveoli c. Extreme increase in pulmonary capillary pressure d. Pulmonary fibrosis
According to Fick's Law of Diffusion, the rate of diffusion across a membrane increases as follows:
- Increased surface area of the membrane
- Increased difference in alveolar pressure (PA-Pa)
- Gas solubility has increased.
- Reduced membrane thickness
Gas diffusion across plasma membranes is involved in respiration.
The lungs of mammals are made up of millions of alveoli, which provide a large surface area for gas exchange. Air enters and exits these alveoli via the same network of airways.
Diffusion transports gas across the alveolar-capillary membrane, as described by Fick's law equation :
movement of gas (Vgas) = membrane's diffusing capacity (DM) × pressure gradient across the membrane (P1 minus P2).
A) Although the percentage of oxygen in inspired air remains constant at different altitudes, the decrease in atmospheric pressure at higher altitudes reduces the partial pressure of inspired oxygen and thus the driving pressure for gas exchange in the lungs.
B) smaller alveolar volumes would reduce the surface area of the thin fluid lining naturally.
C) Increased pulmonary capillary pressure causes more fluid to flow out of the capillaries into the interstitium and, in extreme cases, causes pulmonary edoema. The mean pulmonary artery pressure, pulmonary vascular resistance, and total blood flow all contribute to pulmonary capillary pressure.
D) The lungs stiffen in pulmonary fibrosis due to scarring, which is called fibrosis. This fibrosis makes it more difficult for oxygen to pass through the air sacs in the lung, reducing the amount of oxygen that can enter the bloodstream. Fibrosis stiffens the lungs, causing them to shrink in size and capacity.
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