The epidermis, the outermost layer of skin, contains four main types of cells:
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Keratinocytes: These are the most abundant cells, producing keratin, a protein crucial for skin's strength and waterproofing. Keratinocytes make up the majority of the epidermal layers and undergo a process of differentiation as they move from the basal layer to the surface, eventually becoming dead, flattened cells in the stratum corneum. [Reference: Multiple sources, including StatPearls and DermNetNZ.]
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Melanocytes: These specialized cells produce melanin, the pigment responsible for skin color and protection against harmful UV radiation. Melanin is transferred to keratinocytes, providing a crucial defense mechanism against sun damage. [Reference: Multiple sources, including StatPearls.]
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Langerhans cells: These are immune cells that play a vital role in skin's immune defense. They act as antigen-presenting cells, initiating an immune response against pathogens and allergens that penetrate the skin. [Reference: Multiple sources, including StatPearls and DermNetNZ and PubMed.]
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Merkel cells: Located in the basal layer, these cells are associated with sensory nerve endings, contributing to touch sensation and mechanoreception (the sense of pressure and touch). [Reference: Multiple sources, including StatPearls.]
These four cell types work together to maintain the skin's protective barrier function, provide immune surveillance, and enable sensation. The relative abundance of each cell type varies across different skin regions and layers.
