This is a picture of a person's plica semilunaris, but it is most commonly referred to as the third eyelid. The plica semilunaris is the small fold of tissue located on the inside corner of your eye. A third eye is an example of a vestigial structure. A vestigial structure is a body part or organ that has lost its original function as the species has evolved over time. A third eyelid is is a vestigial structure because the original purpose was to insure that the eye remains moist. As time progressed the third eyelid has decreased in size, which causes it to be unable to fulfill its original purpose.
No comments:
Post a Comment