Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Living things and cells?

  1. Mar 4, 2006 #1
    The textbook says that every living thing is made up of cells.

    What about the shell of a crab or egg shells? Are they inert matter or made up of cells?

    If they are made out of inert matter than how does the organism control their function?
  2. jcsd
  3. Mar 4, 2006 #2


    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    They are made up of cells. The can grow, die and be replaced. Inert matter cannot do that. Same is true of your fingernails and hair, for example.
  4. Mar 4, 2006 #3
    Someone told me that hair was inert and part of skin cells hence they grow because of the cells in the skin commands them to. Wiki only refers hair cells to specialised parts of the body and not to hair on the head or hair on the outside of the body. http://en.wikipedia.org/wiki/Hair_cell
    Last edited: Mar 4, 2006
  5. Mar 5, 2006 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Not true, only the cells in the rim of your fingernails are alive, after that they keratinize and grow outward: that is dead material. The same with hair, hair is not alive: only the root is.

    The egg shell probably calcifies over time and is able to grow in the soft stages in between. Once it is calcified it is not alive.

    The crab grows by molting, where a soft shell grows underneath the hard shell, which is eventually released.

    The outer layer of your skin is not alive either, it is keratinized skin that is shed.
  6. Mar 5, 2006 #5
    Which is what used to make me laugh about those shampoo adverts now I may not be an expert on biology but hair that is dead? Absorbing vitamins? isn't really going to help much now is it? and neither is the root absorbing them. I mean you might as well eat the shampoo. And even then it'll only make a difference if you have some sort of vitamin deficiency probably. It's just a load of chemicles that do all the stuff to your hair. Oh and don't even get me started on face creams:rolleyes:
  7. Mar 5, 2006 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The egg shell was never made of cells, unlike hair which is dead cells. The egg shell is calcium compounds secreted within the oviduct of birds to surround the cellular components within it.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook