5 Facts About Bones You May Not Know

Did you ever break a bone? If you were a child, the doctor may have explained that while your broken limb was in a hard plaster cast, the broken bone was “knitting” itself back together. In a child’s experience, broken things like plastic toys or sticks from trees don’t put themselves back together. They need glue or other substance to fix them. So the repair happening inside your cast was a mystery.

Even today, as an adult, you may not think of your bones as living, dynamic organs. Here are five facts you may not realize:

1. You may think of bones as hard and rigid, but in fact, they have some degree of flexibility. This allows them to “give” a bit when force is applied, in order to resist breaking.
2. The flexibility of bone comes from its composition of two substances: collagen and calcium. The primary material that makes up bone is collagen, the most plentiful protein in our body. Collagen has elastic properties, and it is also found in skin, muscle, tendons, blood vessels and the digestive system. In bones, collagen acts as a soft framework, while the mineral calcium (from calcium phosphate) strengthens and hardens bones.
3. Bones have two types of cells that are responsible for constantly renewing (remodeling) bone. One type, osteoclasts, act to “reabsorb” (resorb) old bone minerals and tissues which are eventually flushed out of the body. The other type, osteoblasts, replaces the old tissues and minerals with new ones. When these two processes are in balance, bone mass is preserved.
4. Bones have their own blood vessels that carry cells and minerals in and out of the bony structure. Thanks to this network, the supplies needed by osteoblasts are brought in, and the old minerals broken down by osteoclasts are taken away for disposal.
5. When a bone is broken, the body wants to begin the “knitting” process right away. There are three overlapping stages in knitting.
• a) Inflammation happens immediately as blood flows into the area and clots. This stabilizes the region of the break and also gives a “framework” for the modeling of new bone.
• b) The clotted blood is replaced first with collagen (to form tissue fibers in what is called a soft callous in and around the break), then gradually minerals are added to compose hard bone. This is ongoing while the cast is on.
• c) Over the next several months, the final remodeling occurs as the healed area becomes compact and returns to a normal form. Blood vessels also form to improve circulation.

So now you have a glimpse into the living, dynamic world of bones. It’s important to keep bones healthy by good nutrition and exercise—especially weight-bearing exercise, which “motivates” bones to keep that right balance between osteoclasts and osteoblasts. Given the important tasks that bones perform and sustain, it’s worth investing in keeping them in well maintained.