РThe epidermis is an epithelium(上皮) comprised of keratinocytes(角质形成细胞) and dendritic cells(langerhans cells朗格汉斯细胞,merkel cells麦克尔细胞,melanocytes黑素细胞).РThe main cells of the epidermis are the keratinocytes (角质形成细胞 80%),which synthesise the protein keratin(角蛋白).Рstratum basale, 基底层Рstratum corneum 角质层Рstratum spinosum 棘层Рstratum granulosum 颗粒层Рstratum lucidum 透明层РThe epidermis (表皮)РStratum basale(基底层): is a major region of mitotic(分裂)activity. The basal layer posed of columnar(柱状) cells which are anchored to a basement membrane (基地膜)?Epidermal transit time(表皮通过时间或更替时间):?New keratinocytes slowly migrate up toward the surface of the epidermis. The process needs 28 days.?From stratum basale to stratum granulosum is 14 days, then to stratum corneum and gradually shed is 14 days. Total is 28 days.
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