What is a key function of the orbicularis oculi muscle?

The orbicularis oculi muscle is primarily responsible for surrounding the eye, which is its key function. This muscle encircles the eye socket and plays a critical role in various facial expressions and functions. By contracting, it allows for actions such as blinking, squinting, and closing the eyelids tightly. These actions are essential for protecting the eye from foreign objects and excessive light, as well as for keeping the eye moist.

The other options pertain to different facial muscles and their distinct roles. For instance, controlling mouth movements relates to muscles like the orbicularis oris, which manage the movements of the mouth. Elevating the eyebrows is primarily the function of the frontalis muscle, while pulling the scalp backward involves the occipitalis muscle. Each of these muscles has specialized functions that contribute to facial expression and movement, but none of them surround the eye like the orbicularis oculi does.