S ay “skeleton” to children and you probably conjure up in their minds a rickety structure of rigid sticks, or, to the more fanciful child, a clickety-clacketing collection of rattling bones cavorting under a Halloween moon. A look at almost any anatomical drawing of the human skeletal system bears out the child's image: dry sticks of bones, stripped of skin and flesh, muscle and tendon—a grotesque caricature of a living human being.
Our living bones are something quite different. They are rigid, yes, but not entirely so: they also may bend a little and grow and repair themselves; and they are shaped and fitted so that—rather than the herky-jerky motions of a wooden puppet—they permit the smooth grace and coordination power displayed by an accomplished athlete or a prima ballerina.
Our bones do not do just one thing but many things. Some bones, like the collarbone or clavicle , mainly give support to other body structures. Others, like the skull and ribs, encase and protect vulnerable organs. Still others, like the metacarpi and phalanges that make up our hands and fingers, give us mechanical advantages—leverage and movement. There are even bones, the tiny ossicles in the middle ear, whose vibrations enable us to hear.
Finally, to think of bone simply as a structural member, like a solid steel girder in a skyscraper, ignores the fact that bone is living tissue. It is one of the busiest tissues in our bodies, a chemical factory that is continually receiving, processing and shipping a wide variety of mineral salts, blood components, and a host of other vital materials.