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| Section2 = | Section3 = }} 7-Dehydrocholesterol is a zoosterol that functions in the serum as a cholesterol precursor, and is converted to vitamin D3 in the skin, therefore functioning as provitamin-D3. The presence of this compound in human skin enables humans to manufacture vitamin D3 from ultraviolet rays in the sun light, via an intermediate isomer pre-vitamin D3. It is also found in the milk of several mammalian species.〔"7-dehydrocholesterol." The American Heritage Stedman's Medical Dictionary. Houghton Mifflin Company, 2002. 21 Jan. 2007. (Answers.com ).〕 In insects it is a precursor for the hormone ecdysone, required for reaching adulthood.〔Ed Yong (2012), Thanks to one gene, this fly needs a cactus to escape Neverland (Not Exactly Rocket Science )〕 It was discovered by Nobel-laureate organic chemist Adolf Windaus. ==Location == The skin consists of two primary layers: an inner layer, the dermis, comprising largely connective tissue, and an outer, thinner epidermis. The thickness of the epidermis ranges from 0.08 mm to greater than 0.6 mm (from 0.003 to 0.024 inches).〔Frediric Martini et al. (2006). Human Anatomy. Pearson/Benjamin-Cummings Publishers, p. 89. ISBN 0-8053-7211-3.〕 The epidermis comprises five ''strata''; from outer to inner, they are the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. The highest concentrations of 7-dehydrocholesterol are found in the epidermal layer of skin—specifically in the stratum basale and stratum spinosum.〔Norman, Anthony W. (1998) (Sunlight, season, skin pigmentation, vitamin D, and 25-hydroxyvitamin D:integral components of the vitamin D endocrine system. ) Am J Clin Nutr;67:1108–10.〕 The production of pre-vitamin D3 is, therefore, greatest in these two layers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「7-Dehydrocholesterol」の詳細全文を読む スポンサード リンク
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