By Ashley H. Robins
Dermis colour could be the main decisive and abused actual attribute of humankind. This e-book provides a multidisciplinary evaluation of the way and why human populations range so markedly of their dermis colour. The organic elements of the pigment cellphone and its creation of melanin are reviewed. The capabilities of melanin within the epidermis, mind, eye and ear are thought of, and the typical medical abnormalities of pigmentation, comparable to albinism, are defined and illustrated. specific reflectance info from all over the world surveys of pores and skin colour also are offered. subsequent, historic and modern backgrounds of the phenomenon are explored with regards to the so-called colour challenge in society. ultimately, the potential evolutionary forces that form human pigmentation are assessed.
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Extra resources for Biological Perspectives on Human Pigmentation
Whenfivehuman subjects (Caucasoid) with abnormal skin hyperpigmentation were treated with 1 gram of melatonin daily for 25-30 days only one patient showed any skin lightening: in the others the skin colour remained unchanged (Nordlund & Lerner, 1977). On the other hand, Rickards (1965) injected melatonin into dogs with canine melanosis and noted a lightening of the melanotic areas within 48 hours with desquamation of dark scales, indicating that melanin deposits were being extruded. In contrast, the function of melatonin is morefirmlyestablished in those mammals which undergo seasonal changes in their coat colour, changes that are predominantly governed by the length and intensity of daylight.
Et al. (1989). ) 3 Aaron Lerner of Yale University Medieal School has dedicated himself to the study of the pigment cell for 40 years. His success in developing the endocrinology of melanin pigmentation has been remarkable, he and his team being the first to isolate both MSH and melatonin. ) 3 Ultraviolet radiation and the pigmentary system The previous chapter discussed the variable influences of hormones on the epidermal melanin unit. The secretion of the pineal hormone, melatonin, is governed by the amount of light reaching the eye and this mechanism enables animals like the weasel and arctic fox to alter their coat colour according to the seasons.
Larger doses had a more pronounced effect on melanogenesis than smaller doses, and also increased the melanocyte count in the anterior abdominal wall (Snell & Bischitz, 1960). In women who had undergone ovariectomy oestrogen administration was found to have increased the skin pigmentation, although this was attributed largely to elevated skin oxyhaemoglobin resulting from a greater cutaneous blood supply (Edwards & Duntley, 1949). Progesterone expands frog melanophores, but its influence in the mammal is less clear.