“Dem bones, dem bones, dem dry bones.”
Remember the old spiritual? Well, bones aren’t dry at all. Rather, they are really quite complex–and remember they are living tissue. Just because they seem sturdy and firm doesn’t mean that they don’t need nutrients and oxygen, just like all the rest of your tissues.
The process of building bone cells starts very early in life–maybe two months or so–and continues until you die although the rate changes a lot.
Bone cells are produced amongst a mixture of minerals, mainly calcium and phosphorus. In hard, or compact bone, the cells are laid down in rings, much like the rings in a tree.
Running through the layers are little tubes called caniculi, which form a transportation network. Blood brings in food and oxygen, and carries off carbon dioxide as well as new blood cells.
During the time it takes to read this sentence, about 10 million of your red blood cells have died. During the same time, the red marrow in your bones has produced about the same number of new ones.
This process goes on as long as you live.
I’m sure you all know your white blood cells (leukocytes) are your main defence against infection. Again, they come from the bone marrow. And that’s not all. The little platelets, which are needed for blood to clot, also are made here.
Pretty important stuff!
The yellow part of bone marrow (which you will find if you break apart a big bone from a beef animal) is a storehouse of fat, which equates to energy. If your body needs energy over a long haul, it can call on this strategic reserve to supply it.
When a bone is broken, it usually starts to heal very rapidly, depending on age of the person. First, a thick tissue layer is formed at the break, then harder stuff called a callus. Also a ring of still harder material grows around the break site to protect it.
Finally a new bone tissue grows in place of the callus until the new part is the same size and shape as the old part was. The temporary materials disappear, and the bone is as good as new.
Bones, like any other tissue, can become diseased. One of the most common problems is arthritis, in which the joints swell and become very painful. Cartilage between the joints is destroyed, and the spaces filled with deposits of calcium.
Joints which are meant to move smoothly are now scraping over these hard minerals.
So “dem bones” are not so simple after all–and they certainly are not dry. They allow us to get around but they do a whole lot of other things, too.
