Physical Fitness and Well-Being Skin Part 1
About physical fitness, medical information, anatomy, well-being and care of your skin.
TAKING A PHYSICAL--HEAD TO TOE
Your skin is one of the largest, most complex systems of your body. In a 3/4-in. square on the back of your hand there are 9 ft. of blood vessels, 30 hair follicles, 300 sweat glands, 600 pain sensors, 6 cold sensors, 36 heat sensors, 75 pressure sensors, 9,000 nerve endings, 13 yd. of nerves, and 4 oil glands.
Skin accounts for 16% of your body weight. The average woman has 17 sq. ft. of skin, the average man, about 20.
About 10% of your blood circulates through your skin.
Your skin has more nerve endings than any other part of your body. Sensations of pain, pressure, heat, and cold are each served by a different kind of nerve ending. All these sensory messages are carried from your skin to your brain.
Skin thickness varies from 1/2 millimeter on sex organs to 6 millimeters on the soles of your feet.
Your skin does basically two things: protects your inner organs from harmful substances in the outer environment and prevents that 60% of you which is water from evaporating.
Your skin produces its own melanin (for instance, when you get a suntan) to filter out the sun's ultraviolet rays, which can harm you. Thus, people from sunny climates evolve dark skins and people from dark climates evolve light skins.
The outmost skin layer, called the epidermis, is made up of dead, flattened cells bound together by natural oils. Epidermis is constantly being rubbed off, but is also constantly being replaced by cells from the skin layer just below it, called the dermis.
The average person sheds about 40 lb. of epidermis in his or her lifetime.
Skin is self-healing, producing its own antiseptics, as well as new skin cells, to close up its wounds quickly.
Your skin prevents harmful bacteria from entering your body. However, bacteria can pass through the pores of your skin, the pores being sweat glands and hair follicles. Acne, boils, and blackheads are examples of diseases created in this way.
Absorption of substances through the skin is limited. Water or solutions with sugar or salt cannot be absorbed. Oils and fats can be, but only to a small extent, seldom past the epidermis.
Lead, mercury, and particular kinds of aniline dyes are harmful substances which can be absorbed through your skin. People working with these materials, take care!
Apocrine glands, located around sex organs, armpits, and nipples, secrete a milky fluid. The fluid, which contains fat, dries to form a thin, gluey substance whose scent is a sexual stimulus.
When the temperature in your body rises, the pituitary gland, located in your brain, secretes hormones which move out through your bloodstream and cause small blood vessels in your skin to open. As this occurs, blood circulating at the surface of your skin loses heat through radiation, lowering the body's temperature. At the same time your sweat glands release fluids, and your skin is cooled as they evaporate. Cool skin means cool blood.
When your body temperature drops, the pituitary gland sends out its hormonal messages to reduce the circulation of blood to the skin. Sweat glands stop releasing fluids, and heat is held in your body.
Goose bumps are caused by the contraction of muscles attached to hair follicles. This makes hairs stand up. The original idea, which is still effective in hairy animals, was to create a kind of fluffy hair blanket, or insulation barrier, against the cold.
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