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.
