THE SKELETAL SYSTEM

The 206 bones of the body make up a working whole called the skeleton, or skeletal system. Together, the bones of the skeleton perform many important functions, some of which have already been mentioned. To summarize:The skeletal system provides support for the body otherwise you would be a shapeless blob of skin covered tissues and organs. It also provides for movement, with individual bones serving as points of attachment for the skeletal muscles and acting as levers against which muscles can pull.Delicate internal structures are protected by the skeleton. The brain, for example, lies within a strong, bony casing called the skull; the rib cage surrounds and protects the heart and lungs.The bones of the skeleton are a storehouse for minerals such as calcium and phosphorus.

Amazingly, bone tissue is continually broken down and reformed, the mineral salts being transported to other parts of the body on demand. In fact, scientists have estimated that your body completely "replaces" your skeleton over a period of 7 years! Lastly, certain inner portions of bones contain red marrow and arc your internal factory of blood cells. Without this factory you would die, since red blood cells have a short life span of approximately 120 days. Without these cells your body would have no efficient means to transport life giving oxygen to your tissues. 'White blood cells are also produced in the red bone marrow. One of the main jobs of certain classes of these cells is to ingest bacteria and debris.