Dem Bones, Dem Bones, Dem Dry Bones! But how do bones grow?

The things we typically thing of as “bones” – the hard, white parts – don’t typically grow.  They’ve already ossified (which is just a fancy way of saying that calcium has been deposited to make them nice and hard).

The long bones (like arm and leg bones) are the best examples to describe bone growth. As kids, like our most dynamic visitors at the Children’s Museum of Houston, our bones are mostly hard. But, near the ends of the bones, are two areas of cartilage. Cartilage is a stiff but flexible tissue. Your ears and parts of your nose are composed of cartilage, which is why you can smoosh and twist them around.

The cartilage in your bones (growth plates in the case of long bones) is the stuff that grows. As it grows, special cells in your body called osteoblasts, cause calcium and other minerals to deposit into the cartilage, making it into bone. But the cartilage is still there! Want to see it?

What You Need:

  • Chicken bones – I recommend the bones from hot wings. The bonus is you get to eat the hot wings! :-)
  • Vinegar
  • A Cup
  • Some time

What to Do:

  1. First, you have to clean the bones. This mean first eating the meat off the bone (or having someone else do it), then gently boiling the bones for about 30-45 minutes.
  2. Once boiled, let the bones cool and then pull off the connective tissues. The boiling helps to soften the tissues and will often remove part of it in the process, but in the end you will need to do some of it by hand.
  3. Place the bones into a cup
  4. Fill the cup with vinegar so the bones are totally covered
  5. Place the cup out of the way. The bones will need to soak for at least 24-48 hours.
  6. Once done soaking, you should be able to gently bend the bone without breaking it. You can always keep a few out of the vinegar for comparison purposes.

What’s Happening?

Vinegar, or acetic acid in scientific terms, reacts with calcium. This reaction removes the calcium from the bones, leaving just the cartilage behind. Like I said, cartilage is a stiff, but flexible tissue. So, you can now bend the bones without breaking them (but if you are too rough, you can tear the cartilage). 

By the way, around your late teens to early twenties, your growth plates will ossify (aka harden) which is when you finally stop growing (upward, at least).