The Secrets to a Good Bone (Part II)

Last time I told you how bone is comprised of mineral crystals called bioapatite (a.k.a. hydroxylapatite) and long fibres of collagen. The bioapatite gives the bone hardness while the collagen gives it toughness and strength against breaking. Together they provide greater resistance to tensile (pulling) and compressive (crushing) forces than either substance on its own. Sometimes the bone is lacking in one of these ingredients and it can have serious health consequences.

People often don’t realise that bone is a living tissue with a rich blood supply as it is constantly being remodelled. We usually only see bones long after the animal died. After death, the living material rots away, including the collagen, resulting in a very dry, fragile material. This dried out bone still contains bioapatite and so is still hard but gone is the toughness provided by collagen.

A child with osteogenesis imperfecta, where the bones lack collagen. Source: ShakataGaNai (Wikimedia)

There is a genetic condition called osteogenesis imperfecta, or brittle bone disease, which results in an insufficient or low quality collagen being made in the bone. In severe forms of the disease the patient is unlikely to survive the first year of life but people with milder forms can go on to live full lives (and are often portrayed in sci-fi and medical shows). The disease is incurable and requires management through physiotherapy and sometimes supplements aimed at strengthening the bone and preventing fracture.

The opposite case would be one where there is a lack of bioapatite in the bone. A simple experiment that demonstrates this involves submerging a chicken bone in vinegar for a few days to a week. One of the chief ingredients of bioapatite is calcium carbonate which is dissolved by the weakly acidic vinegar. The end result is a bone with a rubbery sort of texture that can be easily bent without breaking as it is mostly collagen.

The bowed legs of a child with rickets. Source: Wikimedia

You were probably told as a child to drink plenty of milk, which is high in calcium, to give you strong bones. Calcium is absorbed in the small intestine and used to make bioapatite. You may also have been told to get plenty of vitamin D, which promotes absorption of calcium. Vitamin D is found in eggs and oily fish but the body can also produce its own in skin that is exposed to the UV radiation in sunlight.

A lack of calcium in the bone leads to a condition called rickets and is mostly known for giving the legs a bowed appearance. This is usually the result of a lack of vitamin D preventing calcium absorption. Treatment involves increasing calcium and vitamin D through dietary changes, supplements and increased exposure to UV radiation. If performed early enough it can prevent the changes in bone shape from becoming permanent.

So keep those bones healthy by getting plenty of calcium and vitamin D and do plenty of exercise to work those bones so that they have to stay strong. Hopefully then you’ll be able to avoid getting yourself in a situation like this:

References:

Again, I’ve used my old physiology textbooks, but Wikipedia tends to be just as good.

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2 thoughts on “The Secrets to a Good Bone (Part II)

  1. Pingback: The Secrets to a Good Bone (Part I) « Socks and Thongs Science

  2. If you clicked on the chicken bone experiment link you will have seen that it takes you to a site called Answers in Genesis, a religion based site, and you may be wondering why I would do so, given the incongruity between science and religion.

    To put it simply, of all the sites I found that described this experiment, this site gave the most in depth and scientifically accurate description of what was going on. If you don’t believe in God simply substitute “We can only marvel at the handiwork of God” with “We can only marvel at the handiwork of evolution”.

    As an aside, I don’t understand why people seem to think that believing in God contradicts what we know from science. For instance, you can still believe that humans evolved from early primates (and whatever else evolved from/into whatever else) and still say that God was behind it all. Its simply a matter of believing that God meant for it to be a process that nature went through to get to humans. I know some people have trouble with this concept as it involves not taking a literal interpretation of everything in the bible, but it is possible if you open your mind to all the possibilities.

    I’d like to point out that I myself have no religious affiliations nor do I firmly believe or disbelieve in the existence of God (or Gods). In fact, 90% of my knowledge of religion, particularly christianity, comes from watching The Simpsons, even with my two years at a religious school. Maybe thats why I just want to see a world in which everything can just work together and allow differing beliefs while still agreeing on the fundamentals of what has and is likely to happen.

    End ramble.

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