Why do We Have a Skeleton?

There are two main jobs that the skeleton does it supports the body and it protects delicate organs. The skeleton is the frame that holds man erect. It is made mostly of bones. A baby is born with as many as 270 small, rather soft bones in his framework.

A fully grown person usually has 206, because some bones become fused, or grow together. Bones fit together at joints can be moved freely. For example, when you run, you move your legs at the hip and knee joints.

Some joints cannot be moved at all. At the base of the spine the bones are fused, forming one bony plate that fits into another. Neither moves. The joints in your skull are solid, too, except for those in the jaw.

The protection that the skeleton provides includes the hard, bony cap of the skull. This protects the brain. The rib cage protects the heart and lungs. And the backbone, or hollow spinal column, protects the spinal cord, the body’s trunk line nerve cables.

The backbone is actually a string of a small bones. It is hard for us to think of bone as living tissue, but it is. It grows when a person is young. For example, the thigh bone may triple in length between the time a person is born and the time he is fully grown.

Bones grow in length and thickness as calcium and other minerals are added to them. And since bone is living tissue, it must be fed. The outside of the bone is covered with a thin, tough skin. The skin holds many tiny blood vessels that carry food to the bone cells.

The middle of a bone is spongy and filled with marrow. Some of the marrow is a storehouse for fat, and other marrow makes red blood cells.  

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