Which muscle is responsible for closing the eyelids?

The muscle responsible for closing the eyelids is the orbicularis oculi. This muscle encircles the eye and contracts to help close the eyelids when blinking or squinting. Its action is crucial for protecting the eyes from environmental irritants and maintaining moisture on the surface of the eye by spreading tears.

In contrast, other muscles mentioned do not serve this function. The zygomaticus major is primarily involved in smiling, as it helps elevate the corners of the mouth. The temporalis muscle is a muscle of mastication, involved in chewing by aiding in the elevation and retraction of the mandible. The buccinator is mainly responsible for actions related to chewing, such as keeping food between the teeth and preventing it from accumulating in the cheeks; it does not play a direct role in eyelid movement. Thus, the orbicularis oculi is specifically adapted for the task of eyelid closure.