Keratinization
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Developmental process Keratinocyte differentiation Programmed cell death |
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As cornification (keratinization) is the process of transformation of epithelial cells through horn-forming cells ( keratinocytes ) to horn cells ( corneocytes ). Cornification processes occur physiologically in the epidermis and various mucous membranes and increase the mechanical stability of the surfaces. The formation of horns and horn structures ( hair , nails , hoof , claws ) also takes place via cornification processes.
The cornification process
In the skin, cornification begins in the prickly cell layer ( stratum spinosum ) of the epidermis. This is where the cell's cytoplasm begins to be transformed through increased formation of keratin , keratin-associated proteins and lamellar bodies ( membrane coated granules ). In the granular layer ( stratum granulosum ) the cells lose their nucleus and form keratohyalin , which is packed in granules. A distinction is made between F-granules , which contain profilaggrin consisting of filaggrin , and L-granules with loricrin . In the horny layer ( stratum corneum ), the corneocytes, finally arise. Here the profilaggrin breaks down into filaggrin, which bundles the keratin from the dissolving keratohyalin granules to form tonofibrils . The cells flatten and the nucleus is degenerated.
Cornification disorders
The normal course of cornification is also known as orthokeratosis . Cornification disorders ( keratosis , parakeratosis ), excessive cornification ( hyperkeratosis ) and deficient cornification ( hypokeratosis ) as well as dissolution of the horny layer ( keratolysis ) can occur.
literature
- Alexander Meves: Dermatology intensive course . Elsevier, Urban & Fischer Verlag, Jena / Munich 2006, ISBN 3-437-41162-4 , pp. 17-19.