Keratinocyte

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Keratinocytes (green) in the skin of a mouse

The keratinocyte ( synonym : the horny cell ) is the type of cell that occurs mainly (over 90 percent) in the epidermis . This cell type produces keratin and differentiates itself in the course of cornification , while it moves from the lowest layer of the epidermis to the uppermost layers (which face the outside world). The result is the corneocyte (synonym: the horny cell ).

Histology of a skin layer made up of the dermis and the various layers of keratinocytes

Origin and development

Keratinocytes are derived from epidermal stem cells that are located in the area of ​​the stratum basale or in the area of ​​the outer root sheath of the hair follicle . As they are pushed up by the offspring cells, they wander through several stages of development until they form a layer of flattened, dead corneocytes in the stratum corneum .

The time between differentiation in the stratum basale and exfoliation as a corneocyte in the stratum disjunctum is about a month, but can be in certain diseases, e.g. B. in psoriasis , be shortened.

During this differentiation, the keratinocyte constantly changes its shape and geometric alignment. In the stratum basale , the keratinocytes arise from epidermal stem cells and have an approximately cylindrical shape. In the stratum spinosum , the remodeling of the cells begins with an increase in volume and a change in the cell axis in a more horizontal direction. There are keratohyalin formed and the conversion processes are progressing rapidly. The cells become flattened, the cell nucleus is lost , shrinkage due to fluid loss and finally cornification. Keratinocytes can no longer be detected in the following stratum corneum (horny layer). Keratinocytes became corneocytes.

tasks

The stratum corneum forms a barrier that keeps foreign bodies and germs out and protects the body from dehydration.

Keratinocytes are actively involved in the immune response, inflammatory processes and wound healing. They can produce a wide variety of cytokines , growth factors, and even complement factors . In many chronic inflammatory skin diseases, TNF-alpha and IL-1 in particular , but also many other interleukins and chemokines, are released.

Keratinocytes contribute to UV protection by taking up melanosomes (melanin-containing vesicles ) from melanocytes . The melanin is stored around the cell nucleus and protects it from UV-related damage.

Web links

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