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How many cells are in a human body?
- Katelyn (age 14)
Unionville Missouri United States of America
The answer is 'a whole bunch!'. Wikipedia says there are about 100 Trillion = 1014
of them. You can make a crude estimate, however, without counting all of them. Individual cells can be seen in a microscope and you can measure their size, d, which is about 10 microns.
The volume of a cell is then d3
and its weight is the volume times the density, close to that of water. Putting this all together you get that a single cell has a mass around 10-12
kilograms. Dividing into the weight of a good sized person, 100 Kg , you get the Wiki-number.
(published on 09/08/2011)
Follow-Up #1: Density of human body cells?
don't different cells have different densaties?
- david (age 68)
The two main cell types in the human body are muscle and fat. Muscle cells have a density of about 1.06 times that of water. Fat cells on the other hand have a density of 0.92 .
I'm rather skinny and without some paddling effort will sink in a swimming pool. I have a few pleasantly-plump friends who can float without effort. In sum, the average is not far from 1.
(published on 06/11/12)
Follow-up on this answer.