What are the functions of keratinocytes?

The main purpose of keratinocytes is to make a barrier to protect against microbial, parasitic, viral, and fungal invasion. These cells produce keratin and are also responsible for the generation of the epidermal water barrier by producing and secreting lipids to prevent water loss. Additionally, these cells play a role in signal transduction inside the extracellular matrix. Kerinaoctytes also function to synthesize vitamin D through the activation of cholesterol by UVB light. More specifically, during exposure to sunlight, 7-dehydrocholesterol in the skin absorbs UVB radiation in the epidermis and keratinocytes convert it to previtamin D3, which then isomerizes into vitamin D3. Another function of these cells is that they play a structural role, as they form tight bonds with other cells in the epidermis and maintain them in their locations. Kertinocytes also function as immunomodulators, because of their ability to produce inhibitory cytokines when there is no injury. When there is an injury, Langerhans cells are activated by keratinocytes and rush to the area of infected or cut skin. Another function is that after melanin has been processed by melanocytes, they are moved inside the keratocytes where pigments are retained to provide the skin and hair with color. Keratins are the major proteins that exist in keratinocytes. These proteins assist in the formation of keratinocytes cytoskeleton. Keratin expression becomes altered as transient amplifying cells which differentiate and move towards that stratum corneum, forming as nails and hair.