Esthetics Core Written Practice Test

The epidermis is primarily composed of keratinocytes, which are specialized cells responsible for producing keratin, a protein that provides structure and protection to the skin. In fact, keratinocytes account for about 95% of the epidermal layer. This high percentage reflects their critical role in forming the outer barrier of the skin, protecting against pathogens, and preventing water loss.

Keratinocytes undergo a process of differentiation as they move from the deeper layers of the epidermis to the surface, where they eventually shed off in a process known as desquamation. The other cell types present in the epidermis, such as melanocytes, Langerhans cells, and Merkel cells, contribute to functions like pigmentation, immune response, and sensory perception, but they only make up a small fraction of the total cell population. Thus, the choice indicating that 95% of the epidermis is composed of keratinocytes accurately reflects the predominant role of these cells in skin structure and function.