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Me pretending to be wiser than the scientist specialists

Saturday, June 28, 2008
Some time back, I had read how the bones of astronauts are very weak when they return back to earth after a long stay in space. Then they do all sorts of things to regain bone density and strength.

The speculation is that the bones lose their density owing to lesser gravity. But scientists are not sure of the mechanism involved.

But I wonder,
1) Could it not be something lot simpler, and from the known territory of science, like absence of sunlight and hence absence of vitamin D?
2) Or does this happen inspite of the astronauts taking regular 'vitamin D' suppliments?
3) And anyways, even if they took all the supplements, who said science has discovered all the vitamins, and especially all the vitamins and substances human beings produce by 'photosynthesis' apart from Vitamin D?
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4 comments :

Ketan said...

Well, it doesn't look like you were trying to joke here.

I think, astronauts must be taking vitamin D, supplements. Second, artificial light must also be inducing some vitamin D synthesis at least. Third, vitamin D being fat-soluble one must be taking a few months to get depleted to a critical level. Fourth, vitamin D deficiency you would cause widespread systemic effects, not just decreased bone density.

So, vitamin D deficiency is unlikely to be major contributor to the problem.

What I though know is that the trabeculae in the bone develop negative electrical charge owing to piezoelectric effect when subjected to any of the possible forces--compression, traction, torsion. And ionized calcium being a cation, gets deposited at those negatively charged sites. So lack of weight bearing, significantly reduces those negative charges and leads to loss of calcium. That's why exercises in space crafts somewhat help prevent calcium loss.

Hope this helped. TC.

stupidosaur said...

Hey! Cool explanation man! As a present engineer who once upon a time lived on a hospital campus as kid, and who got equal marks in Maths an Bio in 12th and who kinda wanted to be a vet, I am really delighted by this nugget! piezoelectric effect in trabeculae! Wow!(Piezolelectric effect I remember well, trabeculae sounds familiar, though I forgot what it was :P)

But then there is something more here isn't it? I heard the astronauts do work out in space.

Well as consolation, I heard the condition reverses quickly on coming back to earth.

Ketan said...

Uh-oh!

Oh, I almost got a compliment from you, and I missed it! Well those were the days, I didn't know of RSS feeds. :(

Anyway, you might have already seen what a trabecula is.

Basically, trabeculae are like the individual legs of a tripod stand. It's said that the Eiffel tower was inspired from the internal structure of bones. So that might give you some idea. So basically, trabeculae are aligned such that forces can get transmitted along their long axes. The most predominant force on Earth is of body weight, which manifests as compressive force, such that most of the trabeculae would be oriented to transmit the force vertically downwards. But in space, the exercises would be exert forces through only the tendons (connect muscle to bone) and ligaments (connect bone to bone), which would act only at the surface of the bone, also much weakly than compressive force of body weight. So, exercises would still help preserve calcium to a degree, but not exactly preserve the internal structure (trabeculae supporting weight would be now utilized to withstand the pull of tendons; basically, they'd get re-aligned, but of course many of them would also be lost as calcium in blood and urine).

Last time when I'd commented somehow I never thought the possibility that you could be not connected to life sciences! Your GK is that good! Otherwise, I'd have definitely been more explanatory. I was also worried you should not take me to be demeaning of you by elaborating a lot, and thus indicate my underestimating your knowledge! Hope you understand. :)

TC.

Ketan said...

Your mom/dad are/were in the medical field? Did you join engineering as some kind of compromise? What's your field of graduation?

Sorry for this flurry of questions, but looking at the tone of your above response looked like you would answer! So, why not take chances! :P

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