Use the textbook values in mm Hg: alveoli pO₂ 104 and pCO₂ 40; deoxygenated blood 40 and 45…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Use the textbook values in mm Hg: alveoli pO and pCO ; deoxygenated blood and ; oxygenated blood and ; tissues and .
- Find the gradient of oxygen from the alveoli to the deoxygenated blood.
- Find the gradient of carbon dioxide from the deoxygenated blood to the alveoli.
- Find the gradient of oxygen from the oxygenated blood to the tissues.
- Find the gradient of carbon dioxide from the tissues to the oxygenated blood.
Need a reminder? The key ideaShow
The partial pressure of a gas is its share of the total pressure: . Gases diffuse from the higher partial pressure to the lower one. The rate depends on the gradient, the solubility of the gas and the thickness of the membrane. Carbon dioxide is to times more soluble than oxygen.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. The partial pressures of the table.
Plan. Subtract the lower value from the higher value for each gas.
Step 1. (a) mm Hg, from the alveoli into the blood.
Step 2. (b) mm Hg, from the blood into the alveoli.
Step 3. (c) mm Hg, from the blood into the tissues.
Step 4. (d) mm Hg, from the tissues into the blood.
Answer: , , and mm Hg.
Check. The gradients of oxygen are large, and those of carbon dioxide are small. Carbon dioxide still crosses well because it is far more soluble.
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