The upper surface of the skin is called (a) Epidermis. The epidermis is the outermost layer of the skin, serving as a protective barrier against environmental factors such as pathogens, UV radiation, and dehydration. It is primarily composed of keratinocytes, which produce the protein keratin, along with melanocytes, Langerhans cells, and Merkel cells. The epidermis continually sheds dead skin cells from its surface and undergoes constant renewal through cell division in the basal layer. This layer also contains melanocytes responsible for producing melanin, the pigment that gives skin its color and provides protection against UV radiation.