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The pink corner of your eye is the third eyelid.
Have you ever noticed the pink triangular tissue in the inner corner of your eye? This is called the plica semilunaris, and it is actually a remnant of a third eyelid that some animals have. This third eyelid is called the nictitating membrane, and it helps protect and moisten the eye without blocking the vision. Humans don’t have a functional nictitating membrane, but some other primates do. The plica semilunaris still serves some purposes in humans, such as facilitating the movement of tears and helping the eye rotate.
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