| The human skeleton is a strong, flexible framework of 206 bones that supports the body and protects internal organs. The bones of the skeleton connect at joints to permit a wide range of body movements. Bones come in many shapes and sizes, each adapted to perform specific functions. The breastbone, for example, is a flat plate of bone that helps to protect the heart and lungs in the chest. The fused bones of the skull safely encase the brain. The short, delicate bones in the wrist and hand enhance dexterity, providing considerable flexibility for small, precise motions. The long, heavy bones of the legs serve well as strong levers for powerful or speedy movement. In addition to these structural and mechanical functions, the bones of the skeleton store calcium, a mineral essential for the activity of nerve and muscle cells. The soft core of bone, the bone marrow, is the site where red blood cells, certain white blood cells, and blood platelets form. |
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