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Issue
32— January 2003 |
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32 |
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Titel |
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| Cover
Pictures |
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Skin
pigmentation through sunlight |
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When the human skin is exposed to ultraviolet rays, a biosynthesis of melanin
occurs. Melanin is a brown or black pigment which is produced in the melanosomes
and protects the skin from damaging sun irradiation. Melanosomes are components
of the melanocytes, which are special cells producing melanin (see Figure).
The enlarged part in the figure shows a melanocyte which produces pigments
protecting the skin from damaging UV rays. Melanocytes are located in the
basal cell layer of the epidermis. They form long, finger-like protuberances
(dendrites) which grow into and through the neighboring keratinocytes. Keratinocytes
are originally colorless skin cells.
Under the influence of ultraviolet light, cell components of the melanocytes
fill up more and more with melanin and move further to the periphery of
the cells and into the dendrites. Thus, the keratinocytes are filled up
more and more with brown pigments, and a coloring of the skin occurs (see
right hand side of Figure).
The formation of color pigments has the purpose to protect the skin and
body from the negative influence of intensive sun irradiation. The melanin
pigments filter the ultraviolet rays of the sunlight and thus prevent damages
to the deeper skin layers.
If a protective cream is applied on the skin (see left hand side of Figure), the
skin is additionally protected from damaging UV light. Special light protection
measures are recommended, especially in the snow.
