Physical Fitness and Well-Being Bones Part 2
About physical fitness, medical information, trivia, anatomy, well-being and care of your bones and skeleton.
TAKING A PHYSICAL--HEAD TO TOE
Over 100 bones, or nearly half the bones in your body, are in your hands and feet.
Careful examination of a bone reveals that there are four layers of stuff involved: marrow, at the center; a thickness of spongy bone; a wall of hard, calcified bone; and a thin outer layer of skinlike tissue.
A complex of arteries carries blood in and out of your bones. As blood passes through, it picks up new blood cells which have been manufactured in your bones. The blood also feeds and bathes the cells which make up your bones.
A careful examination of bones reveals that they are thickest at points of greatest stress, thinnest at points of lowest stress. Strength with an economy of weight is the obvious principle of their evolution.
Bones can withstand stresses of 24,000 lb. per sq. in.
People who weigh 130-160 lb. exert about 12,000 lb. of pressure per sq. in. on their thighbone when they're walking.
When your body is in need of calcium, hormones are sent into your bloodstream. These, in turn, cause calcium to be released from storage in your bones, and the calcium then enters your bloodstream.
All the bones in your body manufacture blood cells--red ones, white ones, and platelets. The main factories, however, are your skull, your rib cage, your vertebrae, and your pelvis.
No bone cell in your body is more than 0.1 millimeter from a capillary (tiny blood vessel), thus guaranteeing you that each bone cell in your body will be kept nourished and vital.
In conjunction with muscles, bones act as levers, which greatly expands the capacities of our muscles.
When a bone is broken, the surface of the bone produces its own healing substances. Cells join together to form a soft, calluslike material on the fractured surfaces. Once this bond is formed, new bone grows in that area to repair the break.
The femurs, or thighbones, are the largest bones in your body. The tiny malleus (hammer), incus (anvil), and stapes (stirrups), located in your ear, are the smallest.
If you examine a skull, you'll discover that it seems to be made up of several bones. Where these bones join, you'll see cracks, or seams, which medical scientists call sutures.
Some of these seams, open at birth, continue to seal up all through our lives. The gradual sealing up of the skull starts at about 22 years of age and continues until the age of 81.
Medical scientists can examine the seams of the skull and calculate the age at death of even extremely old skeletons. They do this by knowing the time schedules followed by the human organism in sealing up the skull seams.
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