Keratinization (keratosis) - the emergence Horny substance - scleroprotein (keratin) in the tissues. Keratin contains sulfur (2-5%), sustainable, in conventional solvents not soluble proteins, eosin stained pink, pikrofusin - yellow. Physiologically keratinization occurs in the epidermis. In the cytoplasm of cells granular layer appear small basophilic granules of keratohyalin, the exact chemical composition of which is unknown. Believe that keratohyalin direct participation in the process of keratinization not accept. The first signs of O. planned in the cells of glossy layer. Cell cytoplasm impregnated with a homogeneous, brilliant, highly refracting light acidophilus substance-seidina considered to be intermediate between keratohyalin and keratin. Before Acting grains of keratohyalin how would disappear, the body cells with a new, original fibrous keratin, which, closing, converted into a dense homogeneous mass of keratin. In orogovevshi cells kernel flattened, killed, hollow Horny scales dry up and fall. Scales stanovily, their cavities contain air and fatty substances - oleic acid and cholesterol. In parallel scales are replaced orogovevshie cells from the underlying layers. A person keratinization especially intensively occurs on the palms and soles, weaker at the place of bend. To Horny formations are derived epidermal: hair and nails person; hair, hoof, horn mammals; birds feathers; the scales of reptiles. Abnormal keratinization can be caused by a number of endogenous and exogenous causes and expressed in hyperkeratosis (see), parakeratosis, heterotopic O., wrong embryonic development rudimentary squamous epithelium. Acting can be also dermoid, teratoma, squamous cell cancers.