Anatomy & Physiology Worksheet With Answers Page 20
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22Station J: Skin
91. – 95. What pigments are responsible for skin color and what factors are involved in skin color?
How does UV light affect the skin
Skin Pigments - three pigments are responsible for skin color- melanin, carotene,
hemoglobin – genes, sun exposure, volume of blood in the capillaries and RBC
unoxygenated blood determine skin color
Melanin is located mostly in epidermis
Number of melanocytes are about the same in all races
Difference in skin color is due to the amount of pigment that melanocytes produce and
disperse to keratinocytes.
Freckles are caused by the accumulation of melanin in patches
Liver spots are also caused by the accumulation of melanin
Melanocytes synthesize melanin from an amino acid called tyrosine along with an
enzyme called tyrosinase. All this occurs in the melanosome which is an organelle in
the melanocyte.
Two types of melanin: eumelanin which is brownish black and pheomelanin which is
reddish yellow
Fair-skinned people have more pheomelanin and dark skinned people have more
eumelanin
UV light increases enzymatic activity in the melanosomes and leads to
increasedmelanin production.
A tan is achieved because the amount of melanin has increased as well as the darkness
of the melanin. (Eumelanin provides protection from UV exposure while pheomelanin
tends to break down with too much UV exposure)
The melanin provides protection from the UV radiation but prolonged exposure may
cause skin cancer.
96. – 100. How does aging affect the skin and the glands and accessory organs within the skin?
Beginning in our 20s, the effects of aging begin to be visible in the skin.
Stem cell activity declines: skin thin, repair difficult
Epidermal dendritic cells decrease: reduced immune response
Vitamin D3 production declines: calcium absorption declines and brittle bones
Glandular activity declines: skin dries, body can overheat
Blood supply to dermis declines: tend to feel cold
Hair follicles die or produce thinner hair
Dermis thins and becomes less elastic – wrinkles
Sex characteristics fade: fat deposits spread out, hair patterns change
Genetically programmed chronologic aging causes biochemical changes in collagen
connective tissues that give skin its firmness and elasticity.
The genetic program for each person is different, so the loss of skin firmness and
elasticity occurs at different rates and different times in one individual as compared with
another.
As skin becomes less elastic, it also becomes drier.
Underlying fat padding begins to disappear.
With loss of underlying support by fat padding and connective tissues, the skin begins to
sag. It looks less supple and wrinkles form.
The skin may be itchy with increased dryness. A cut may heal more slowly.
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