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How do keratinocytes move from the basal layer to the surface of the epidermis?
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human skin
Human skin, whose cells are generated continuously by the body, serves as a protective barrier between the inside of the human body and the environment.
Keratinocytes are continuously formed in the lower region of the epidermis through mitosis, primarily within the basal layer (stratum basale). As new cells are produced, they are pushed peripherally toward the skin surface, undergoing a series of well-defined changes as they transition through the layers of the epidermis.123
The progression of these cells follows this general path:
- Stratum Spinosum: Newly formed cells move into the prickle-cell layer, where they are knit together by desmosomes.13
- Stratum Granulosum: As cells move into the granular layer, they accumulate granules of keratohyalin. In this layer, membrane-coating granules migrate to the cell periphery and discharge waxy lipids into the intercellular spaces.13
- Stratum Corneum: Finally, the cells reach the horny layer, where they lose their nuclei and organelles, become flattened, and fill with keratin.13
The entire process, from formation to the eventual shedding (desquamation) of dead cells at the surface, typically takes one to three months.2