third eyelid
Noun: * A protective fold of skin or membrane in the inner corner of the eye of some animals, which can be drawn across the eyeball for protection or moisture. It is also known scientifically as the nicitiating membrane.
The term "third eyelid" is used specifically in zoology and veterinary science to describe an anatomical feature found in certain animal groups. It is not a feature of human anatomy. * It functions as a protective shield. * It helps to moisten and clean the eye's surface.
- The bird used its third eyelid to protect its eye from dust while flying.
- A visible third eyelid in a cat can sometimes be a sign of illness.
- Reptiles often have a well-developed third eyelid that acts like swimming goggles underwater.
- The third eyelid is often more translucent or transparent than the main eyelids, allowing for some vision while it is deployed.
- In veterinary medicine, the condition where the third eyelid is permanently or abnormally visible is called "cherry eye."
- Nicitiating Membrane (n): The formal, scientific term for the third eyelid.
- Haws (n, plural): A common, informal term used particularly for the visible third eyelid in dogs and cats.
- Nicitiating membrane
The "third eyelid" is not a separate, fully-formed eyelid like the upper and lower lids. It is a specialized fold of tissue. While common in birds, reptiles, and many mammals (like cats, dogs, and sharks), it is vestigial or absent in humans and other primates.
- a protective fold of skin in the eyes of reptiles and birds and some mammals