PSI Barbering Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

The outermost layer of the epidermis is the stratum corneum. This layer is composed of dead, flattened skin cells that are continuously shed and replaced. Its primary function is to serve as a barrier to protect underlying layers of skin from environmental factors such as pathogens, chemicals, and physical injury. The stratum corneum also helps to prevent water loss, maintaining the skin's hydration and overall health.

The other layers, such as the stratum lucidum, stratum spinosum, and stratum basale, are all located beneath the stratum corneum and play different roles in skin health and regeneration. The stratum lucidum, for instance, is found only in certain areas of the body, like the palms of the hands and soles of the feet, and provides an additional layer of protection in these high-friction areas. The stratum spinosum and stratum basale are involved in the processes of cell production and providing strength to the skin structure but are not exposed to the external environment like the stratum corneum.