Miles (age 7) asks “How come when you pull your hair out it doesn’t bleed even though it’s inside your body?”

hair follicle copy

Miles, my friends drifted of the question slightly so I would like to add a few words. Firstly no experiment this time. We cannot have you tearing your hair out looking for bloodstains. You can see from the diagram that the hair is attached to the blood system so it is very likely that removing it would create a very, very small bleed. This would most likely be contained within the follicle (the follicle is the gland/cavity in which the hair grows) so you will not be able to see it.

Hair also goes through three stages of development. In the first stage it is growing quite fast and this can last for up to 5 years. In the second phase the hair growth is transitionary. It will only last for a couple of months but during that time it loses its blood supply, so pulling it out will not cause bleeding. In the third phase the hair starts to fall out on it’s own. As you are seven years old it is likely that you have all of these phases going on at the same time.

Many thanks Miles – a fascinating question.

4 thoughts on “Miles (age 7) asks “How come when you pull your hair out it doesn’t bleed even though it’s inside your body?”

  1. Great question, Miles. I learned something too. My hypothesis about the dermis and epidermis wasn’t exactly right.

  2. Thank you for answering my question science master and friends!
    How come as you grow older your hair changes color – is it a 4th phase?

  3. The colour comes from a pigment called melanin. This pigment is put into the hair just before it leaves the surface (epidermis). It is put in by cells called melanocytes. It is thought that as you get older the melanocyte cells begin to die so less pigment enters the hair.

    It seems similar to a lot of cell activity as somebody gets older.

  4. How fascinating! 🙂 Great question. ..those trips up and back alone with Cian are times I always treasure! They are bonding moments. I will pass on The Science Master website to Randy!!!
    How did you find it? So sorry we couldn’t get the boys together! One year Cian and I were discussing the planets and Pluto and I was surprised about something Cian knew and he told me I had read it to him in a book about planets the year before!!! Ha! Life is made up of teachable moments. .. if only people would learn from them!!! 🙂

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