A keratinocyte is a type of cell found in the outer layer of the skin, known as the epidermis. These cells are responsible for producing keratin, a tough protein that helps protect the skin from damage, pathogens, and water loss. Keratinocytes make up about 90% of the cells in the epidermis and play a crucial role in maintaining the skin's barrier function. As keratinocytes mature, they undergo a process called keratinization, where they move from the deeper layers of the epidermis to the surface. During this process, they become flattened and filled with keratin, eventually forming a protective layer of dead cells. This layer is essential for skin health and helps prevent infections and dehydration, contributing to the overall function of the integumentary system.