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166026.  Sat Apr 14, 2007 8:53 am Reply with quote

Update on the smallest cell front. I caused an argument between a histologist and a pathologist in the pub last night; they couldn't decide whether platelets are cells or not. Anyway, they're both independently checking it out with their hospitals' haemotologists, so hopefully I'll have an answer in a week or so.

Anyway, if anyone has access to JTSOR, can you check this article out?

The Vacuolation of the Blood-Platelets: An Experimental Proof of their Cellular Nature

It contains the sentence:

As a matter of fact, studying the question from another aspect also shows that their vacuolation is proof that the blood-platelets are cells.

166030.  Sat Apr 14, 2007 9:08 am Reply with quote

Quite a few places seem to refer to them as 'cell fragments' althrough they do seem to have all the characteristics, and carry out all the requisite functions, that cells do.

There are some human-symbiotic bacteria (many times more than the number of human cells, in fact) that may be smaller than 1.5Ám. I'm having a search...

166031.  Sat Apr 14, 2007 9:10 am Reply with quote

yeah, I agree with that. And that's kinda what one of my friends was saying - if you include platelets as cells, then there's all sorts of smaller stuff that you may have to start including.

166032.  Sat Apr 14, 2007 9:11 am Reply with quote

Yep - these are much smaller (~0.3Ám):

166035.  Sat Apr 14, 2007 9:25 am Reply with quote

While I agree that symbiotic bacteriae are important in a healthy human, I think it's a stretch to most people to claim that they are part of 'the human body'.

166042.  Sat Apr 14, 2007 9:43 am Reply with quote

They're healthy in a live human. It's not just your stomach flora (although you'd die without them) - it's practically everything else.

Most of you isn't 'your body'. Practically every single cell inside you is host to several other bacteria. Your mitochondria, for example, which give you your energy, have their own DNA. They just happen to live inside us, and without them, we wouldn't exist.

There's always been a bit of fudging when it comes down to defining what 'an organism' is, because everything above the level of bactrium is basically a symbiotic arrangement of other, separable and identifiable organisms that live co-dependently.

And as you couldn't even remotely live without your bacteria, it makes sense to think of them as 'part of you'.

166044.  Sat Apr 14, 2007 9:47 am Reply with quote

I've never understood why gut flora aren't called gut fauna?

166049.  Sat Apr 14, 2007 9:58 am Reply with quote

They're bacteria, so, strictly speaking, they're not either. Odd, though, that whoeveritwas chose the plant name.

166051.  Sat Apr 14, 2007 9:58 am Reply with quote

I quite like the idea of asking what percentage of you is plant rather than animal.

166055.  Sat Apr 14, 2007 10:10 am Reply with quote

I agree with all that Gray, and maybe it's just a semantic thing, but I think many of our viewers would feel cheated if we claim that an organism which can live ouside the human body is "part of the human body". If we said "smallest cell in the body", then I suppose it works to have a bacteria as the answer.

I wonder if everyone has mycoplasma in their body, or whether it is only a percentage of the population? Indeed are there bacteria that all humans have? I seem to remember reading a while ago that many species are unique to each human. Like your bacteria-print is like a tiny dental record.

166361.  Sun Apr 15, 2007 2:36 pm Reply with quote


The Oxford Dictionary of Biochemistry and Molecular Biology agrees that platelets are cells.


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