The term for the outer layer of skin is the epidermis. The epidermis is the thin, protective outer layer that serves as the body's first line of defense against environmental factors such as pathogens, UV radiation, and physical injury. It consists mostly of keratinocytes, which produce keratin, a protein that gives the skin its toughness and resilience. The epidermis also contains melanocytes that produce melanin, contributing to skin color and protection against UV damage. While the epidermis lacks blood vessels, it receives nutrients from the underlying dermis, maintaining the skin's health and functionality in regulating hydration and sensation.