Final answer:
The skin functions to prevent water loss, block the entry of microorganisms, and synthesize vitamin D.
Step-by-step explanation:
The skin has multiple roles in the body. Many of these roles are related to homeostasis. The skin's main functions include preventing water loss from the body and serving as a barrier to the entry of microorganisms. Another function of the skin is synthesizing vitamin D, which occurs when the skin is exposed to ultraviolet (UV) light. Melanin in the epidermis blocks some of the UV light and protects the dermis from its damaging effects.