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Author Topic: Why, and how, does hair grow?  (Read 3312 times)

Offline gjanssen

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Why, and how, does hair grow?
« on: 12/07/2009 11:55:13 »
My grandson (5) asked me: "Grandad, why does hair grow?"

Does anyone knows?

Gerard Janssen, The Netherlands
« Last Edit: 20/07/2009 09:00:43 by chris »


 

Offline JnA

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Re: Why, and how, does hair grow?
« Reply #1 on: 12/07/2009 13:01:44 »
Hair grows because that's what it's programmed to do.

How it grows is a different story.. basically it starts from the part of the hair just under the skin. The base of the hair follicle (the hole in your skin the hair sits in) is given food and energy by the blood (as well as some other things) this food helps the hair to add layers, which makes it taller (just like when you eat food and grow taller, except your layers are inside your bones and muscles) As the hair grows taller it becomes longer on the part that you can see.  After a little while the blood stops feeding the hair and it falls out.. but you always have new hair surrounding it growing, so you might not notice it falling out very much.

How's that?

« Last Edit: 12/07/2009 15:14:36 by JnA »
 

Offline gjanssen

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Re: Why, and how, does hair grow?
« Reply #2 on: 12/07/2009 16:47:45 »
Thanks for the explanation, but I think the answer is more on 'how' hair grows than 'why' hair grows. Rethinking the question it might be a very existantial matter that can be divided in two parts.

1. Why do humans have hair?
2. Why does it grow?

Maybe I am complicating the case, but I do believe that it is worth it.

Gerard Janssen
 

Offline Pwee

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Re: Why, and how, does hair grow?
« Reply #3 on: 13/07/2009 14:06:08 »
Hair is an excellent protective barrier. It protects from physical injuries, keeps animals warm, provides camouflage, works as an extention of the skin for providing touching sensation and so on. It's a great thing.
Seeing all these benefits, the real question is why DON'T humans have more hair. For this, I don't really know the answer, I can just guess:
Maybe through our evolution these protective functions slowly lost their value, but the downsides were still there.
Some of these downsides of hair is: it provides excellent shelter and breeding ground for parasites. The other is that it needs some energy to maintain and grow.

On the question that why does it grow, the answer is simple, because of its protective functions and its placement (outside our skin) it is put out to the "destructive" forces of the environment it's subjet to abrasion.

Another interesting question is why do we still have hair on the places we have and why we don't have hair on other places of our body. I know that pubic hair and hair in the armpit is important for some of our communication with smell. We preserve sweat and so smells on these places, so our partners can get some indispensable information about the state of our body (sexual arousal, maturity, illnesses, in women - ovulation etc.)
 

Offline gjanssen

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Re: Why, and how, does hair grow?
« Reply #4 on: 13/07/2009 19:57:54 »
Thanks very much for the answer. This solves the case.
Now it's my turn to translate it to my granson.

Gerard Janssen
 

Offline JnA

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Re: Why, and how, does hair grow?
« Reply #5 on: 15/07/2009 16:23:59 »
JnA Answer Fail.


 

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Re: Why, and how, does hair grow?
« Reply #5 on: 15/07/2009 16:23:59 »

 

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