What is the outermost layer of the epidermis called?

The outermost layer of the epidermis is known as the stratum corneum. This layer plays a crucial role in the skin's barrier function, as it is composed of dead skin cells that are constantly shed and replaced. The stratum corneum provides a protective barrier against environmental factors like pathogens, chemicals, and physical abrasions. It also helps to prevent moisture loss, allowing the skin to maintain hydration.

In contrast, the other layers of the epidermis do not serve as the external protective barrier that the stratum corneum does. The stratum granulosum contributes to the process of keratinization, the stratum lucidum is found only in certain thick skin areas, and the stratum basale is where new skin cells are generated. Each of these layers has important functions, but it is the stratum corneum that forms the first line of defense for the skin.