What is the main function of keratinocytes in the skin?

Keratinocytes are the predominant cell type found in the epidermis of the skin and are primarily responsible for producing keratin, a structural protein that plays a crucial role in protecting the skin. The main function of keratinocytes is to create a waterproof barrier that helps prevent water loss and protects against environmental damage, pathogens, and physical injury. As they migrate from the deeper layers of the epidermis to the surface, keratinocytes undergo a process called keratinization, where they become more filled with keratin and eventually die, forming the outer protective layer of the skin.

While other cell types in the skin serve different functions, such as melanocytes which produce melanin for pigmentation and protection against UV radiation, or Merkel cells that are involved in sensation, the primary role of keratinocytes centers around producing keratin for skin protection. This is why the option referring to keratinocytes producing a protein to protect the skin is the correct answer.