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Medical How Human growth works?

  1. Aug 31, 2008 #1
    I want to know how our genes limits and define our growth, I mean, how the osteoblastos knows that they must stop or continue, how our cells knows when to stop growing or dividing, etc.
    Every human has a unique "morphology", the bones and skull has their own and particulary morphology, but their are created by individual cells, which are very similar between differents humans, therefore, why we have so many differents anatomy? who is (and how) controlling the work of this cells (like osteoblastos).
    Thanks !!!
    PS: sorry for my bad english, I hope you understand my question anyway =(
  2. jcsd
  3. Sep 1, 2008 #2
    That's a very tough question with potentially allooot of explanation that a geneticist pretty much devotes his career to. You'll want to understand more about genetics and biochemistry. I'll try to keep this brief and very simple (Correct me if I'm wrong on anything).

    Basically, genes are like an instruction booklet. Cells read this and make proteins. Proteins perform basically all the functions of the body. In the case of bone osteoblasts, they will help take up, organise and lay down all the minerals that make up bone. When there is enough bone, the proteins can feel it due to some chemical/molecular feedback, and they send a signal back to the genes, telling it to switch off. In terms of overall bone structure, bone stop elongating at a certain age because the cells responsible for elongation have a genetic timer that basically tells it to stop. This stuff is all being researched very intensely, the answers are still appearing.

    The question of how cells know when to stop growing is much harder to answer because of the diversity of cells in the body. Skin cells and stomach cells for example continually divide and grow until they die and get replaced all through our life. Many other cells however stop dividing at a certain age or after a certain number of replications. This is now attributed to the shortening of the ends of DNA (telomeres), as with each DNA replication that occurs during division, the ends are not fully copied. Once it reaches a limit, the cells know to stop dividing.

    Now to the question of uniqueness. Every human may share the same overall genetic instructions to live, but some of the letters may be changed around (neutral substitution/genetic drift). This can give rise to slightly different instructions at different places in the body, even though the overall proteins are the same.

    Hope that helps
  4. Sep 1, 2008 #3
    Thanks jaseh86 !
    I know it's a difficult question :-(
    I have some knowledge about genetics and biochemistry (I'm studing Bioengineering). But I can't figure out how a simple cell knows when to stop and when to start again...
    I mean, we start with just one cell, and then we finish with a system really complex of organs. If I need to create a skull, adding little balls (supose they are cells...), then I must first to know what is a skull, and then I need to see it carefully every time I add a new "cell", in that way I will know when to stop. But our cells seems to know perfectly the shape of every organ and structure of our body... and they don't have eyes to see if the construction is well directed.
    mmmm... suppose a "nose", there are many differents shapes... so, what's defining at mollecular levels those shapes? if you have a wide nose, why your osteoblasts doesn't stop before? (or why they do if you have a very little one...).
    I can't understand where are the signals, they seems to be like workers, constructing a building from inside... but a worker can see, hear, talk, think!, a cell is just action-reaction... then who's is controlling the construction and how?

    Thanks again !!!
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