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Within a single species, how does the relative number of cells in the body relate to the relative size of the organism?

Let's say we take two humans, one of them is 6 feet tall and the other one is 5 feet tall. They have similar BMI, age, physical condition, genetic background (aside from height) and are the same sex.

Does the tall one have more cells? Or does he have bigger cells?

PS: Ideally, answers should be backed up by appropriate sources.

PPS: While I'm grateful to everyone for the very nice answers I got, I should point out that I'm waiting for an answer which includes references to accept it.

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In retrospect, I have presented a false dichotomy. As jarlemag has pointed out, a tall person may have neither more cells nor bigger cells - their height (or size, see discussion in buzrw's answer) may be due to more non-cellular mass (eg. more ECM). –  Superbest Apr 18 at 20:37
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4 Answers 4

This is really the most fundamental concept of Cell Biology, so good question. If you look at the size of a any cell from a whale and compare it to the size of any of cells from a mouse, they are in fact quite similar, despite the extreme difference in the overall size of the organisms they are from. There is a reason why cells are small, and it has to do with the fact that they survive based on their ability to absorb enough nutrients from their environment. As a cell gets larger it needs more to survive (because it has a bigger mass). A bigger cell has also has a larger surface area around it (so it can absorb more nutrients).

HOWEVER, there gets to be a point where the mass of the cell is too large for the surface area to compensate for. Mathematically this is shown by what is called the "surface-area-to-volume ratio". Basically, it states that as a a sphere gets larger, the volume increases at a higher RATE than the surface area. So there is a reason cells get only so big, the 60's horror movie The Blob was not scientifically accurate, a single-cell that large (the blob) would not have enough surface area to absorb enough nutrients to sustain itself. Taller (or bigger) people have more cells (not bigger ones) than others.

Effects of osmotic pressure can alter cell size slightly.

When you are talking about taller individuals, you are (I think) really meaning larger people, people with a higher mass. And yes, they have more cells.

Another topic of Cell Biology you may want to explore is apoptosis. Let's say you have two individuals both 180 lbs. one of them is 5' tall and the other 7'. Both these individuals have the same number of cells, but the taller one has a higher percentage of them in the superior and inferior regions of the body. It is the process of apoptosis that sculps an organisms shape.

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You are correct that I, in effect, meant "larger people", because I specified that their BMI is similar. –  Superbest Apr 8 at 19:05
+1 sounds like a good answer for the cell biologist that I am NOT. You may add some elements about how (and why) cell size varies from one species to another. This article also might be of interest. –  Remi.b Apr 9 at 17:26
@Remi.b I'm not sure if that paper applies to my question per se, but it was a fascinating read! Thank you. –  Superbest Apr 18 at 20:33
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Not sure it is proven, but this paper makes use of the assumption: West et al, PNAS 99:2473, http://www.pnas.org/content/99/suppl_1/2473.full

Btw, this paper may be relevant for you as it focuses on the metabolic activity, which is not quite propotional to body mass (power 3/4: it's growing slower)

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The taller person has more cells. Most cells can only lengthen up to a certain point. Whilst the neuronal cells will be longer and likely some others, the rest of the cells will just be of larger number.

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Just to play the devil's advocate, are there actually any sources that confirm this? Couldn't it also be that tall people have the same number of cells, but with more extracellular matrix and larger spacing between the cells? –  jarlemag Apr 8 at 9:20
@jarlemag That's a very good point (which I originally missed); I added a comment to my question to clarify. –  Superbest Apr 18 at 20:37
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Good question... so the condition is height not width. remember the more taller a person is, the more chondrocytes of epiphysial plate (disk) has prolifrated and calcified (in the 12-17) (puberty phase) because you know every long bone has two epiphysial plate distal and proximal and the will be calssificated so it's the chondrocytes that prolifricates (do mitotic division) and increase it's number of cell. so every long bone do this surely it will be increase in number of cells. again it has direct connection with hormones suchas(calcitonin,parthormone,HGh,testostrone. you said that compare two humans which have the same genetics,age,sex. it will not make any sense if you say that these two people have the same conditions and yet they don't diverse it has to do something with factors such as weather,food intake,injuries,depression.so it's nonsense to say if two men are like identical in everything in life such as (genetics,age,sex,metabolism,weather,concentration and impact of hormones,level of depression,injuries) and still diverse in height that would be foolish. so the answer is yes taller people have more cells than

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