Final answer:
The epidermis contains stem cells, keratinocytes, melanocytes, Langerhans cells, and Merkel cells, all contributing to skin protection, pigmentation, and sensation. Keratin and extracellular lipids provide a waterproof barrier and additional protection.
Step-by-step explanation:
Layers and Cell Types of the Epidermis
The epidermis is the outer layer of the skin, playing a crucial role in protection, pigmentation, and sensation. Its primary cell types include:
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- Stem cells: Located in the basal layer, they divide to form new keratinocytes.
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- Keratinocytes: These cells make up approximately 90% of the epidermal cells and produce keratin, a protein that forms a protective, waterproof layer on skin surface.
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- Melanocytes: Produce melanin, providing pigmentation to the skin and protecting against UV damage.
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- Langerhans cells: Immune cells that help fight pathogens.
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- Merkel cells and discs: Sensory receptors that respond to light touch.
Each type of cell contributes to the overall function of the epidermis. For example, keratinocytes form a protective barrier, while melanocytes protect against harmful UV radiation. The stratum corneum, the epidermis's outer layer composed of dead keratinocytes, sheds periodically to make way for newer cells. Meanwhile, extracellular lipids present between the cells provide additional waterproofing. The deeper layers of the epidermis, such as the stratum basale, contain stem cells that continuously reproduce to maintain the skin's integrity.
Overall, these components work together to protect the body from environmental hazards, prevent water loss, contribute to the skin's immune response, and provide sensory functions.