Summary: The primary cell type in the outermost layer of the skin, responsible for producing keratin.
Keratinocytes are specialized epithelial cells that make up about 90–95% of the cells in the epidermis, the outermost layer of the skin. Their main function is to produce keratin, a structural protein that helps form the skin’s barrier against environmental damage such as pathogens, UV radiation, and water loss. Keratinocytes originate in the basal layer of the epidermis and gradually move upward through different stages of differentiation. As they migrate, they produce lipids and proteins that contribute to the skin's protective barrier. At the skin surface, mature keratinocytes become part of the stratum corneum, the layer of dead, flattened cells that are eventually shed through natural exfoliation. Keratinocyte activity is central to skin regeneration, wound healing, and response to inflammation.