Anatomy and Physiology: The Bones

The Bones

Skeleton is an interesting word; big fat weddings aside, the name comes from the Greek word skeletos, which means “dried up body.” This might make sense when you see desiccated mummies with skeletal features due to the loss of moisture, but one look at the true nature of the skeleton and you will see that this is all wrong. Bone is actually very much alive, very moist (50 percent water), and ever-changing.

Some bones grow for your entire life, while others stop growing in your twenties. In order to do their job, bones come in an astonishing variety of shapes. The number of ways bones can break is just as varied. These incredible living organs have a remarkable capacity for fixing themselves, and the marks they leave bear silent witness to our fractured pasts.

Function Junction

In the Oscars there's always an interesting separation between Best Actor and Actress and Best Supporting Actor and Actress. Unlike glitzy awards shows, however, it should be known that bones do more than act in the shadows in a supporting role. The functions of the skeleton include …

• Support. An organism our size would not be able to stand without the strong framework provided by bone.
• Protection. As you will see, there are numerous delicate structures—brain, spinal cord, and so on—that rely on the skeleton to protect them.
• Motion. In providing a place for muscle attachment, for both the moving bone and for the stationary bone, the skeleton makes movement possible.
• Mineral storage. As I discussed, the crystal matrix (mostly calcium and phosphate crystals) of bone provides an ideal storage site, one which is drawn on and added to, as needed, to maintain homeostasis.
• Energy storage. If you have ever seen someone crack open a chicken bone and slurp on the marrow, then you have seen, first hand, the fat-rich yellow marrow (rich in adipose tissue).
• Hemopoiesis. Whaaaat? Wait a minute, hemo, as in hemoglobin? Yes. Hemopoiesis is the production of blood cells (both red and white). This occurs in the red marrow.