In humans, oxygen and carbon dioxide are exchanged in the blood within many smal

Question

In humans, oxygen and carbon dioxide are exchanged in the blood within many small sacs called alveoli in the lungs. Alveoli provide a large surface area for gas exchange. Recent careful measurements show that the total number of alveoli in a typical pair of lungs is about 480 × 106 and that the average volume of a single alveolus is 4.2 × 106 m3. (The volume of a sphere is V=43r3, and the area of a sphere is A=4r2.)

If we assume that alveoli are spherical, what is the diameter of a typical alveolus?   

Explanation / Answer

We know that, volume of a sphere is

V=(4/3)*3.14r3

Now, volume of a single Alveoli is given.

So,

4.2*106=(4/3)*3.14r3

r=100 um

So diameter will be,

D=200*10-6 meters

Or D=0.2mm

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