| "Ultraviolet (UV) radiation is
| |
| | American Academy of Dermatology does not
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| responsible for 90% of the visible signs
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| | recommend their use.UV-B radiation, which
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| of aging on the skin of whites," says Dr.
| |
| | is partially filtered by the ozone,
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| Michael J. Martin, former Assistant
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| | penetrates the skin to the bottom layer
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| Clinical Professor in the Dept. of
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| | of the epidermis where the basal cells
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| Epidemiology and Biostatistics at
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| | are produced. UV-B can break the
|
| University of California, San
| |
| | molecular bonds, disturbing the dividing
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| Francisco.Blacks' skin, however, ages
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| | cells and altering their structure.
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| much slower.Why are most dark-skinned
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| | Compared with UV-A, UV-B is responsible
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| blacks protected from harmful UV rays?
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| | for most of DNAs damage. It also causes
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| Because compared to whites, blacks
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| | most sunburns. During a sunburn the
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| possess more melanin, the pigment that
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| | reddening of the skin, erythema, is
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| gives skin its color.MelaninMelanin
| |
| | caused by dilation of capillaries.More
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| offers protection against UV rays for
| |
| | UV-B is present during summer months
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| blacks and other dark-skinned people.
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| | between 10 a.m. and 4 p.m. and at
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| Conversely, fair-skinned people are much
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| | latitudes closer to the equator.
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| less protected and more susceptible to
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| | Furthermore, at high altitudes the air is
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| skin cancer. Furthermore, albinos' skin
| |
| | thinner and cleaner, so UV-B radiation is
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| offers no protection.Although blacks'
| |
| | more abundant.UV-C, which is generally
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| skin produces more melanin than whites',
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| | filtered by the ozone, has the shortest
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| all skin has the same number of
| |
| | wavelength and the most energy, or
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| melanocytes, the cells that manufacture
| |
| | intensity. It can sterilize hospital
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| the melanin.Melanocytes manufacture
| |
| | equipment and kill bacteria.In addition,
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| melanin from an amino acid, tyrosin, with
| |
| | UV light that reaches the earth is
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| the help of an enzyme, tyrosinase. In the
| |
| | scattered in all directions, and up to
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| bottom layer of the epidermis above the
| |
| | 85% is reflected from surfaces.The Theory
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| dermis, UV light stimulates the
| |
| | of Melanin for Environmental
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| production of melanin in the form of
| |
| | AdaptationOriginally, people of a
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| insoluble melanosomes. These surround the
| |
| | particular race resided in a particular
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| epidermal cells, which move up to the
| |
| | area. As time went on, their skin adapted
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| surface of the skin. The result is a
| |
| | to the environment. For instance, people
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| tan.Blacks' skin produce more melanin,
| |
| | who lived geographically close to the
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| even in the absence of sunlight, and
| |
| | equator had darker skin, and people who
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| their type of melanin, eumelanin, is more
| |
| | lived far from the equator had lighter
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| effective at blocking solar rays.
| |
| | skin.In Scotland, which lies at a
|
| However, white skin produces melanin only
| |
| | northern latitude, descendants of the
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| in the presence of sunlight and after the
| |
| | Britons have white skin. When their skin
|
| UV rays have penetrated the lower portion
| |
| | is exposed to the meager sunlight, the
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| of the epidermis and have caused skin
| |
| | scant amount of melanin their skin
|
| damage."Melanin also functions as an
| |
| | produces is unable to block the sunlight.
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| excellent free radical scavenger. It
| |
| | Therefore, their bodies are able to make
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| affects the delicately designed lipids
| |
| | Vitamin D with the help of sunlight.
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| that hold moisture in the stratum corneum
| |
| | Vitamin D, a vitamin found in fish oil,
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| (the outermost layer of the epidermis).
| |
| | is necessary to prevent rickets, a bone
|
| If the skin loses its moisture, it
| |
| | disease caused by too little calcium.In
|
| becomes rigid and cracks," says Sergio
| |
| | contrast, in Africa, which is near the
|
| Nacht, PhD., Senior Vice-President of
| |
| | equator, blacks require intense sunlight
|
| Enhanced Derm Technologies, Inc. in
| |
| | to penetrate their dark skin to make
|
| Redwood City.UV Radiation and SkinUV-A
| |
| | Vitamin D. This is all well and good.
|
| has the longest wavelength, is not
| |
| | However, when blacks lived in England
|
| filtered by the ozone and passes through
| |
| | during the Industrial Revolution, they
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| glass. It reaches the earth all year long
| |
| | were the first to develop symptoms of
|
| and the amount is comparatively stable.
| |
| | rickets, such as retarded growth, bowed
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| It can penetrate the skin down to the
| |
| | legs and fractures because not enough
|
| dermis, beneath the four layers of
| |
| | sunlight was available.Fortunately, in
|
| epidermis. It is responsible for most of
| |
| | 1930, Vitamin D was discovered and
|
| the visible signs of aging, due to damage
| |
| | dispensed as a supplement to add to the
|
| to collagen and elastic fibers of the
| |
| | diet.On the other hand, the skin of
|
| connective tissue of the dermis.UV-A
| |
| | whites in Australia are in complete
|
| radiation also plays a role in the
| |
| | opposition to their climate.
|
| development of sunburns and skin cancer.
| |
| | Consequently, intense UV radiation has
|
| Tanning salon lamps emit a large amount
| |
| | been the major cause of skin damage and
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| of UV-A rays to generate tans, so the
| |
| | skin cancer Down Under.
|
