Library · Anatomy
Epidermis
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The epidermis is the outermost layer of the skin, the one you touch. It is not a single sheet: it is built from several stacked strata and several kinds of cells.
At the very bottom is the basal layer, home to stem cells that divide nonstop and keep turning out keratinocytes, the cells that fill the epidermis. Those keratinocytes move up. They change as they rise, and at the top they form the stratum corneum, a roof of twenty to thirty layers of keratin, a tough protein, and of keratinocytes that are already dead, flattened into flakes. Skin renews itself from below: a cell is born at the bottom and ends up as a flake at the surface.
The keratinocyte does not only make keratin; it also makes the lipids, the fats, that seal the epidermis and form its water barrier. And among those cells is another one with a different job: the melanocyte, which synthesizes melanin, the skin's main pigment.
In brief
The epidermis is the outermost layer of the skin, made up of several strata and different cell types.
Its strata run from the basal layer, with stem cells that turn out keratinocytes nonstop, to the stratum corneum, twenty to thirty layers of keratin and dead keratinocytes.
Skin renews itself from below: a cell is born at the bottom and ends up as a flake at the surface.
The keratinocyte is the dominant cell and makes the keratin and the lipids of the water barrier; the melanocyte synthesizes melanin.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingAnatomy, Skin (Integument), Epidermis, StatPearlsPublished
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