Keratinocyte

The keratinocyte (synonymous with the horn -forming cell) is in the epidermis (outer skin ) is mainly ( about 90 percent) occurring cell type. This cell type produces keratin and differentiated in the course of keratinization, while he ( the face of the outside world ) of the lowest layer of the epidermis to reach the uppermost layers. As a result, the corneocyte (: the horny cell interchangeably ) is created.

Origin and development

Keratinocytes derived from epidermal stem cells, the basal or are in the area of the stratum in the region of the outer root sheath of hair follicles. You wander through while being pushed by the cells descendant upward several stages of development, until they form in the stratum corneum, a layer of flattened, dead corneocytes.

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

During this differentiation of the keratinocyte is constantly changing its shape and geometric alignment. In the stratum basale keratinocytes arise from epidermal stem cells and have a generally cylindrical shape. In the stratum spinosum of the conversion of the cells with an increase in volume and a change in the axis of the cell begins in a more horizontal direction. Are formed keratohyalin and the conversion processes proceed rapidly advancing. This leads to flattening of the cells, the loss of the cell nucleus, the shrinkage due to fluid loss and, finally, to keratinization. In the following stratum corneum (horny layer) can no longer be detected keratinocytes. From keratinocytes were corneocytes.

Tasks

The stratum corneum provides a barrier that prevents foreign particles and bacteria and protects the body from drying out.

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

Keratinocytes contribute to UV protection by absorbing melanosomes (melanin -containing vesicles) of melanocytes. The melanin is mounted to the cell nucleus and protects it from UV-induced damage.