During gas exchange in the lungs, several factors affect the rate of gas diffusi
ID: 514752 • Letter: D
Question
During gas exchange in the lungs, several factors affect the rate of gas diffusion across alveolar (the alveoli are tiny air sacs in the lungs) and tissue membranes. One of the factors is the difference in partial pressures of the gases across the membranes. The gases will diffuse from an area of high partial pressure to an area of low partial pressure. Look at the illustration below and note which blood vessels carry blood away from the lungs (arterial blood) and which blood vessels carry blood to the lungs (venous blood). The numbers on the diagram are the partial pressure of O_2 and CO_2 (mm Hg) in each of the areas shown. Use the diagram above to explain why oxygen diffuses from the alveoli into the blood and from the Wood into the tissues of the body. Use the diagram above to explain why carbon dioxide diffuses from the tissues into the blood and from the blood into the alveoli and then finally cut into the atmosphere. In certain lung ailments such as emphysema, there is a decrease m the ability of oxygen to diffuse into the blood. How would the partial pressure of oxygen in the blood change? Why does a person with emphysema sometimes use a portable oxygen tank?Explanation / Answer
(13) Gases diffuse from an area of high partial pressure to an area of low partial pressure. According to the diagram, the partial pressure of oxygen in alveoli of lungs is 159 mm Hg. In the arterial blood, the partial pressure of oxygen is 100 mm Hg. For this reason, oxygen diffuses from the alveoli into the blood. The partial pressure of oxygen in tissues is 30 mm Hg and it is lower than partial pressure of oxygen in blood. For this reason, oxygen diffuses from the blood into the tissues of the body.
According to the diagram, the partial pressure of carbon dioxide in the tissues is 60 mm Hg whereas the partial pressure is much lower in venous blood (46 mm Hg). For this reason, carbon dioxide diffuses from the tissues into the blood. The partial pressure of carbon dioxide is further lower in the alveoli. For this reason, carbon dioxide diffuses from the blood into the alveoli and then finally out into the atmosphere.
(14) Partial pressure of oxygen in the blood increases than the partial pressure in the alveoli. For this reason, during emphysema, there is a decrease in the ability of oxygen to diffuse into the blood.
During emphysema the partial pressure of oxygen is low, for this reason patients often use portable oxygen tank to intake oxygen and this increases the concentration of oxygen and also increases the partial pressure of oxygen for proper diffusion of oxygen from alveoli to blood and then from blood into the tissues of the body.
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