THE SKELETAL SYSTEM BONES

 THE SKELETAL SYSTEM BONES FORM the basic framework-the skeleton or chassis-of the body. The primary purpose of the framework is to provide support for the rest of the body through a combination of strength to resist great pressure and flexibility to absorb some shock without shattering. By means of rib cage and skull such vital organs as the heart and brain are guarded. Obviously, the skeletal system is important. Obviously, too, it is a source of much trouble-witness spinal disk problems and the proneness some people have toward easy bone fracture. Yet it is possible to use simple preventive measures to help maintain a healthy skeletal system. Much of the trouble people have is avoidable trouble.

THE BONES Generally, there are 206 bones in the body, although about 5 percent of people have an extra, or thirteenth, pair of ribs, and a much smaller percentage have only 11 pairs. At birth, there are actually about 350 bones, some of which later fuse. The fusion is usually complete by the end of the growth period. Each arm has 32 bones: a collarbone, shoulder blade, humerus, radius, ulna, 8 wristbones, 5 metacarpals in the palm, and 14 phalanges (3 to each finger, 2 to the thumb). Each leg has 31: hipbone, femur, kneecap, tibia, fibula, 7 tarsals in instep and heel, 5 metatarsals in the foot, and 14 phalanges (3 to each toe except for 2 to the biggest toe, the hallux).

The axial skeleton has 80 bones: there are 29 in the head, of which 8 are in the cranium, 14 in the face, 6 in the ears, and 1 in the throat between lower jaw and upper larynx; the spine has 33 bones in all-7 cervical, 12 dorsal or thoracic, 5 lumbar, 5 sacral vertebrae forming 1 bone, and 4 coccygeal vertebrae which, with the sacrum, are fused into one bone (thus, everyone is born with 33 vertebrae but in later life has only 26); there are also the 25 bones in the chest: the breastbone and 24 ribs.