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University of Toronto Scarborough
Larry Sawchuk

EXAM REVIEW SKIN COLOR Lecture 1. skin color is an interactions of cell function, bio-chemistry and geography 2. skin function: -protect muscle tissue -important for immunological response -thermoregulation (through sweating) -vitamin D synthesis -protection against ultraviolet ray (UV) 3. layers of skin - epidermis(most outer layer):  important for skin pigmentation  keratinocytes (basal cells)  it is the predominant cell of epidermis, the formation of barrier that fight against the environment pathogens - dermis (innermost layers)  contain collagens fibbers (strength), nerves, swear glands, hair follicles, and blood vessels. - Melanin (biological polymers)  Determinant of skin color  produced by melanocytes, located at the lowest level of epidermis  melanin are contained in melanosomes (an organelle of melanocytes), and they move to the upper layer of epidermis. (*melanin molenosome molanocytes)  skin color is depend on how much melanin is distributed and rate of melanin synthesis (how active the melanocytes are)  # of melanocytes are same across population  melanin are regulated by MC1R (receptors) that leads the production of the black and brown pigments eumelanin.  Eumelanin  one of the melanin type  produce brown/black  produce when tyrosinase is presented (the more eumelanine, the darker skins you will have)  Phaeomelanin  another type of melanin  produce pink/red  produce when cysteine is presented 4. photospectrumeters  quantitative measure of skin color 5. skin color and genetics. (slides 11,12,13???) 6. skin colour preference (sexual dimorphism and selection)  Example: japan culture prefer lighter skin assertive mating  Lighter women tend to mate with higher status men  Avoidance of sun exposure in the upper classes  Development of discrimination against the darker-skinned in both sexes 7. What trait are selected for in males and females?  Why having lighter skin is more advantageous for women to attract man? 1. because Lighter skin evolved with neotenous traits-sexual attractant(?) 2. Melanin production is controlled by the anterior pituitary, which also secretes the gonadotropins signalling fecundability among women 8. Why is there sexual dimorphism in skin colour in most societies? (slide 18??) 9. The inadequacies of the this theory (sexual selection)  Observers are bias because researchers are white males.  Esthetic preferences are capricious and therefore, require no explanation 10. cold injury hypothesis  individuals with dark skin pigmentation are more susceptible to cold injuries, thus lighter skin are favor in cold weather.  selective force are operated: less attracted/ more prone to have infectious disease/ increase mortality of infants/ decrease reproductive fitness of adult. 11. vitamin D hypothesis (Murray, later Loomis)  V-D is important : it facilitate the absorption of calcium( for bone growth), also neurological function, cancer defense, immune system etc.
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