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In humans, they constitute 90% of epidermal skin cells. [1] Basal cells in the basal layer ( stratum basale ) of the skin are sometimes referred to as basal keratinocytes . [ 2 ] Keratinocytes form a barrier against environmental damage by heat , UV radiation , water loss , pathogenic bacteria , fungi , parasites , and viruses .
Keratosis pilaris (KP; also follicular keratosis, lichen pilaris, or colloquially chicken skin. [ 1 ] ) is a common, autosomal - dominant , genetic condition of the skin's hair follicles characterized by the appearance of possibly itchy , small, gooseflesh -like bumps, with varying degrees of reddening or inflammation. [ 2 ]
Cells in the epidermis contain a structural matrix of keratin, which makes this outermost layer of the skin almost waterproof, and along with collagen and elastin gives skin its strength. Rubbing and pressure cause thickening of the outer, cornified layer of the epidermis and form protective calluses, which are useful for athletes and on the ...
Because of the differences between mucous membranes and the skin (e.g., keratinizing mucosa does not have a stratum lucidum and non keratinizing mucosa does not have this layer or normally a stratum corneum or a stratum granulosum), sometimes specialized texts give slightly different definitions of hyperkeratosis in the context of mucosae.
Parakeratosis is a mode of keratinization characterized by the retention of nuclei in the stratum corneum. [1] In mucous membranes, parakeratosis is normal. [2] In the skin, this process leads to the abnormal replacement of annular squames with nucleated cells.
An example is the skin on the forearm, which is on average 1.3 mm in males and 1.26 mm in females. [4] One average square inch (6.5 cm 2) of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than 1,000 nerve endings. [5] [better source needed] The average human skin cell is about 30 μm in
Skin malignancy, although rare, is reported from all types of porokeratosis. Squamous cell carcinomas have been reported to develop in Mibelli's type porokeratosis over partianal areas involving anal mucosa. This was the first report mentioning mucosal malignancy in any form of porokeratosis.
Dyskeratosis is abnormal keratinization occurring prematurely within individual cells or groups of cells below the stratum granulosum. [1] Dyskeratosis congenita is congenital disease characterized by reticular skin pigmentation, nail degeneration, and leukoplakia on the mucous membranes associated with short telomeres. [2]