Information about Keratinocyte
The keratinocyte is the major cell type of the epidermis, making up about 90% of epidermal cells. The epidermis is divided into four or five layers (depending on the type of skin) based on keratinocyte morphology:
Keratinocytes originate in the basal layer from the division of keratinocyte stem cells. They are pushed up through the layers of the epidermis, undergoing gradual differentiation until they reach the stratum corneum where they form a layer of enucleated, flattened, highly keratinized cells called squamous cells. This layer forms an effective barrier to the entry of foreign matter and infectious agents into the body and minimises moisture loss.
Keratinocytes are shed and replaced continuously from the stratum corneum. The time of transit from basal layer to shedding is approximately one month. Although that approximate time frame can be accelerated in conditions of keratinocyte hyperproliferation, such as psoriasis.
- stratum basale (at the junction with the dermis)
- stratum spinosum
- stratum granulosum
- stratum lucidum (only present in thick skin - i.e. palms of hand and soles of feet)
- stratum corneum
Keratinocytes originate in the basal layer from the division of keratinocyte stem cells. They are pushed up through the layers of the epidermis, undergoing gradual differentiation until they reach the stratum corneum where they form a layer of enucleated, flattened, highly keratinized cells called squamous cells. This layer forms an effective barrier to the entry of foreign matter and infectious agents into the body and minimises moisture loss.
Keratinocytes are shed and replaced continuously from the stratum corneum. The time of transit from basal layer to shedding is approximately one month. Although that approximate time frame can be accelerated in conditions of keratinocyte hyperproliferation, such as psoriasis.
See Also
Epidermis is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface and is made up of stratified squamous epithelium with an underlying basal lamina.
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Stratum germinativum (also stratum basale or basal cell layer) is the layer of keratinocytes that lies at the base of the epidermis immediately above the dermis.
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The dermis is a layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many nerve endings that provide the sense of touch and heat.
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In the skin, the stratum spinosum is a multi-layered arrangement of cuboidal cells that sits beneath the stratum granulosum. Adjacent cells are joined by desmosomes, giving them a spiny appearance when the cells shrink during the staining process while the desmosomes hold firm.
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In microscopic views of skin, the stratum granulosum layer of the epidermis lies between the stratum spinosum below and the stratum lucidum above in stratified squamous keratinized thick skin of palms and soles.
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stratum lucidum (Latin for "clear layer") is a thin, clear layer of dead skin cells in the epidermis, and is named for its translucent appearance under a microscope. It contains a clear substance called eleidin, which eventually becomes keratin.
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The stratum corneum ("horny layer") is the outermost layer of the epidermis (the outermost layer of the skin). It is composed mainly of dead cells that lack nuclei. As these dead cells slough off, they are continuously replaced by new cells from the stratum germinativum (basale).
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Stem cells are primal cells found in all multi-cellular organisms. They retain the ability to renew themselves through mitotic cell division and can differentiate into a diverse range of specialized cell types.
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Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a "type". The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions.
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Keratins are a family of fibrous structural proteins; tough and insoluble, they form the hard but nonmineralized structures found in reptiles, birds, amphibians and mammals. They are rivaled as biological materials in toughness only by chitin.
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Psoriasis
Classification & external resources
A young man whose back and arms are affected by psoriasis.
ICD-10 L 40.
ICD-9 696
OMIM 177900
DiseasesDB .htm 10895
MedlinePlus .
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Classification & external resources
A young man whose back and arms are affected by psoriasis.
ICD-10 L 40.
ICD-9 696
OMIM 177900
DiseasesDB .htm 10895
MedlinePlus .
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Amphiregulin is a member of the EGF family of proteins. Amphiregulin is a major autocrine growth factor for cultured human keratinocytes and probably plays a role in the aberrant keratinocyte growth of hyperproliferative disorders.
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