Colorado Esthetician Written Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Keratinocytes are the most common type of skin cells found in the epidermis. Their primary function is to produce keratin, a protein that helps keep the skin strong, flexible, and waterproof. Keratin is essential for forming the protective outer layer of the skin, known as the stratum corneum. This layer acts as a barrier against external factors such as dehydration, pathogens, and mechanical damage. Therefore, the correct answer is A.

Option B is incorrect because pigment-producing cells are actually melanocytes, not keratinocytes. Melanocytes are responsible for producing melanin, the pigment that gives skin its color.

Option C is incorrect because immune support is primarily provided by specialized cells in the immune system, such as macrophages and T cells, rather than keratinocytes.

Option D is incorrect because keratinocytes do not undergo mitosis to replenish skin cells. Instead, they are continuously produced by stem cells located in the basal layer of the epidermis.