Biological Perspectives on Human Pigmentation by Ashley H. Robins

By Ashley H. Robins

Pores and skin colour might be the main decisive and abused actual attribute of humankind. This booklet provides a multidisciplinary review of the way and why human populations range so markedly of their dermis colour. The organic facets of the pigment phone and its construction of melanin are reviewed. The features of melanin within the pores and skin, mind, eye and ear are thought of, and the typical medical abnormalities of pigmentation, comparable to albinism, are defined and illustrated. special reflectance facts from around the globe surveys of dermis colour also are offered. subsequent, old and modern backgrounds of the phenomenon are explored with regards to the so-called colour challenge in society. ultimately, the prospective evolutionary forces that form human pigmentation are assessed.

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There is therefore no justification for sunbathing in order to achieve a normal vitamin D status. Effects of UV-A This is sometimes referred to as 'long-wave ultraviolet' because at its longer end it impinges on the visible spectrum of light (see Fig. 2). The amount of UV-A reaching the earth's surface is several orders of magnitude greater than the amount of UV-B. UV-A has weak erythema-producing effects compared with UV-B (1000 times less) and, although it does stimulate melanin pigmentation, the resultant tan appears to be more transient and less protective against Photoimmunology 45 UV-induced injury than the one following exposure to UV-B.

Types of ultraviolet radiation (UV) UV is part of the electromagnetic spectrum and it lies between the visible and X-ray regions (Fig. 2). Of the total radiant energy received by the earth from the sun, only 5-10 per cent is in the ultraviolet, the remainder being divided between the visible (about 40 per cent) and the infrared (about 50 per cent). Different wavebands in the UV spectrum show different capacities to cause biological injury. It is thus useful to subdivide UV into three segments, and the following classification will be used in this text: UV-A: wavelengths 320-400 nm UV-B: wavelengths 280-320 nm UV-C: wavelengths 200-280 nm 42 Types of ultraviolet radiation (UV) 43 Fig.

1. 6 Todaeftf/. 4 Olson et al. 09* Toda et al (1972) Olson et al (1973) Everett et al (1979) Olson et al (1973) Everett et al (1979) Toda et al (1972) Toda et al (1972) Everett et al (1979) Todaetal (1972) Toda et al (1972) Toda et al (1972) Olson etal. (1973) Everett et al (1979) Everett etal (1979) Presumably unexposed, although not stated in published study. * Thesefiguresrepresent the average of thefivelargest melanosomes. c Skin samples were taken from three Amerindian tribes - the Kiowa, Comanche and Caddo.

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