What is the main function of the epidermis?

The main function of the epidermis is to protect underlying tissues. This outermost layer of skin serves as the body's first line of defense against environmental factors such as pathogens, chemicals, and physical abrasions. The epidermis is made up of multiple layers of cells, primarily keratinocytes, which produce keratin, a tough protein that strengthens the skin and aids in this protective function.

Additionally, the epidermis plays a critical role in preventing water loss, thereby helping to maintain hydration of the underlying layers. This barrier function is essential for the overall integrity and health of the skin. The other options, although they relate to different skin functions or structures, do not describe the primary role of the epidermis itself. For instance, while adipose tissue is responsible for storing fat, temperature regulation is mainly a function of the dermis and the body's overall response mechanisms. Similarly, the production of hair and nails occurs in more specialized structures and is not a function of the epidermis alone.