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Discussion » Questions » Science and Technology » The hair on your head never stops growing....yet the tiny hair on your body crows only to a certain length and stops...

The hair on your head never stops growing....yet the tiny hair on your body crows only to a certain length and stops...

If you shave the hair on your body ,it will regrow to a a few millimetres and stop....How do hairs on your body know when there are the right length...? 

Posted - April 6

Responses


  • 3311
    Wait... if the  hair on my head never stops growing, then why am I nearly bald?????

    Seriously... if I remember my science, it has something to do with resting phases (?).  Head hair has a short resting phase (when the follicle stops growing) - 20-30 days (I think), while other hair follicles have a longer rests.  Hair on other parts of the body gets broken off easier (due to clothing) than head hair.

    Also, there is no such thing as gray hair.  Hair is normally semi-transparent.  However, each follicle produces pigment which "colors" the hair.  Over time, follicles lose this pigment.  Due to light refraction, we see "gray" hair. This post was edited by Shuhak at April 6, 2019 1:11 PM MDT
      April 6, 2019 10:15 AM MDT
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  • 11516
    I see a Grey Hare the other day...it looked like it was chasing a big Wuffy Wabbit ...:(
      April 6, 2019 12:47 PM MDT
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  • 3311
    I remember my mom having had a shirt that read "one more gray hare".  Below the words were 4 black rabbits and 1 grey rabbit.
      April 6, 2019 1:24 PM MDT
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  • 42751
    The same way the skin knows how to stretch.  The same way the brain stops growing at a certain point.  The same reason toes grow shorter than leg bones. 

    GENETICS.  


    This post was edited by ORANGE FART GOT NO HEART at April 6, 2019 1:11 PM MDT
      April 6, 2019 10:17 AM MDT
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  • 11516
    Well ,my brain must be as big as a Pea now and must have a long way to grow on me...:)
      April 6, 2019 12:49 PM MDT
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  • 1117
    Its a nice question. I know its weird to say , but if you cut/shave some hairs somewhere on your body, it will make the hairs grows even more after it...

    For example, on my butt.... I cut the hairs when its long but it keep growing back. So sometimes its not a win-win situation.
      April 6, 2019 1:13 PM MDT
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  • 25831
    Are you sure?

      April 6, 2019 1:16 PM MDT
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  • 11516
    Am I ever sure...:( 
      April 6, 2019 4:38 PM MDT
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  • 6173
    A follicle will produce new cells for a certain period of time depending on where it is located on your body.  (The hair follicles on your head are programmed to let hair grow for years at a time.)  This period is called the growth phase. Then it will stop for a period of time (the rest phase), and then restart the growth phase again.

    When the hair follicle enters the rest phase, the hair shaft breaks, so the existing hair falls out and a new hair takes its place. Therefore, the length of time that the hair is able to spend growing during the growth phase controls the maximum length of the hair.

    The cells that make the hairs on your arms are programmed to stop growing every couple of months, so the hair on your arms stays short. The hair follicles on your head, on the other hand, are programmed to let hair grow for years at a time, so the hair can grow very long.

    Animals that shed have hair follicles that synchronize their rest phase so that all of the follicles enter the rest phase at once. This way, all of the hair falls out at one time. A dog that sheds will lose its hair in large clumps. Many animals can also switch the coloring agent in the hair follicle on and off -- so in the summer, the hair is pigmented ­brown with melanin (see How Sunburns and Sun Tans Work to learn about melanin), but in the winter it is not pigmented, leaving the hair white.

    (unintended pun, apparently---the arctic hare is white in winter:  The Arctic hare is the largest hare in North America. Its fur is grayish-brown in the summer. It has short ears with black tips. In the winter, it has all white fur, except for the black tips on its ears. Its white fur helps camouflage it from predators in the winter. In the northernmost parts of its range, it is always white.  https://nhpbs.org/natureworks/arctichare.htm)

    https://health.howstuffworks.com/skin-care/hair-care/scalp-treatments/question100.htm

    This post was edited by tom jackson at April 6, 2019 5:01 PM MDT
      April 6, 2019 1:26 PM MDT
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  • 11516
    That was interesting reading....thanks..:)
      April 6, 2019 4:35 PM MDT
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  • 6173
    I enjoyed it as well---I looked it up because it was something I wanted to remember the explanation for.
      April 6, 2019 8:02 PM MDT
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  • 11516
    Well,top marks for looking it up....I wonder how long it took for those people  to work that all out :)
      April 7, 2019 1:43 AM MDT
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  • 6173
    I wonder too.   Isn't the internet amazing?---I can do in 15 minutes at home what used to take an afternoon in the library when I was a teenager.
      April 7, 2019 10:47 AM MDT
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  • 11516
    True....:)
      April 7, 2019 10:50 AM MDT
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  • 279
    Thank God they stop growing at certain length else half of our lives would spoil waxing here and there!!
      April 7, 2019 5:04 AM MDT
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  • 11516
    There are far better ways then waxing...I tried it once and thought  #[email protected]  that ....the other way is far less painful  I found .....  :) 
      April 7, 2019 5:22 AM MDT
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  • 279
    Yeah I know but in any case you have to spend time with that.
      April 7, 2019 5:30 AM MDT
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  • 11516
    Only for a while....lol...
    Its hair today gone tomorrow....lol
      April 7, 2019 5:42 AM MDT
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