• Question: how do bones grow?

    Asked by chloetaylorx to Damien, Rachael, Simon, Suzi, Tim on 16 Jun 2011. This question was also asked by gail07.
    • Photo: Suzi Gage

      Suzi Gage answered on 14 Jun 2011:

      Hi @chloetaylorx
      Thanks for this question. Just this weekend I was at Cheltenham Science Festival talking about bones, so I should know this 🙂

      Bones can only grow at either end. There is cartilage on either end of your bones (called a growth plate), and when the cells on the outside divide and multiply, they push older cartilage cells in to the middle close to the bone, and when these die they are replaced by bone. When the bone reaches it’s full length, the growth plates also turn in to bone.

      Hope this answers your question 🙂

    • Photo: Damien Hall

      Damien Hall answered on 16 Jun 2011:

      I think I know the answer to this (or some of it) from when I broke my leg when I was a child. When a bone is broken, the broken ends form a substance called callus, which eventually melds together and hardens to become new bone. Does that answer the question? Not sure!

Comments

  • Photo: Anna

    Anna commented on :

    Hi cloetaylorx,
    When we’re babies, we have many more ‘bones’ than adults do. As Suzi says, they are mainly made out of cartilage which is a bit bendy. These cartilage ‘templates’ or bone-shapes have blobs of bone in the centres of them, which gradually grow out towards the ends. At the ends of the bones, where the joints are (for example, the knee and the hip of the thigh bone), there are other, separate blobs of cartilage with bony centres. These are called ‘ossification centres’. Bone is gradually laid down by bone forming cells called osteoblasts within these centres. So, the ossification centres grow and the cartilage template gradually is turned into bone from the middle outwards. The blobs at the end of the bones (at the joints) are called ‘epiphyses’, and these gradually fuse onto the main shaft of the bone as you grow, making a whole bone. We reach skeletal maturity at about the age of 25, give or take a few years, and this is when all of the epiphyses of all of the bones have fused to the ossification centre.
    Here’s a nice diagram of what happens : http://training.seer.cancer.gov/anatomy/skeletal/growth.html
    I hope that helps!