A keratinocyte is the principal cell type of the epidermis, the outermost layer of skin. They make up approximately 90% of the epidermal cells in humans.
Keratinocyte Characteristics and Types
Keratinocytes are not a single homogenous type of cell; they undergo differentiation as they move from the basal layer to the surface of the skin. This differentiation process leads to variations in appearance and function.
- Basal Cells: Located in the lowest layer (stratum basale), these are the only keratinocytes that actively divide, constantly producing new cells.
- Prickle Cells (Spinous Cells): These are found above the basal cells and are held together tightly by desmosomes, intercellular attachment points. They represent a stage of keratinocyte maturation.
Different keratinocyte types also express different keratin proteins. These keratins are types I and II intermediate filaments which contribute to the structural integrity of the skin and its appendages. Studies have even identified different clonal types of keratinocytes with varying growth capacities. These differences are reflected in their distinct roles in processes like skin wound healing and immune response. Their capacity for growth and differentiation also makes them essential in skin cancer development.
The continuous production and differentiation of keratinocytes ensure the constant renewal of the epidermis, forming a protective barrier against environmental damage.
