What is "eyelid"?

The eyelid is a movable skin fold that covers and protects the delicate structures of the eye. It consists of thin layers of skin, muscles, and connective tissue. The primary function of the eyelid is to shield the eye from external factors such as dust, light, and foreign objects, while also helping to distribute tears across the surface of the eye. The eyelids can blink rapidly to keep the eye moist and to clear away any irritants. Additionally, the eyelids play a role in expressing emotions, such as blinking in response to bright light or closing during sleep.