A crocodile's third eyelid flushes tears across the eyeball to lubricate its passage and to clean and protect the eye.
Eversion of the nictitating membrane is a condition in which the third eyelid protrudes.
Later, she had a real breakthrough when she discovered that prions collect in pockets of lymphoid tissue in a sheep's nictitating membrane, or third eyelid.
Crocodilians' eyes are immobile spheres covered by three eyelids: the third eyelid, the nictitating membrane, is transparent, but protects the eye from water.
These membranes, essentially a third eyelid, can cover the exposed portion of the eye, since, as in all sharks, the upper and lower eyelids of catsharks cannot completely cover the eyeball.
Definition of third eyelid in US English:
third eyelid
noun
informal
another term for nictitating membrane
Example sentencesExamples
Crocodilians' eyes are immobile spheres covered by three eyelids: the third eyelid, the nictitating membrane, is transparent, but protects the eye from water.
A crocodile's third eyelid flushes tears across the eyeball to lubricate its passage and to clean and protect the eye.
These membranes, essentially a third eyelid, can cover the exposed portion of the eye, since, as in all sharks, the upper and lower eyelids of catsharks cannot completely cover the eyeball.
Eversion of the nictitating membrane is a condition in which the third eyelid protrudes.
Later, she had a real breakthrough when she discovered that prions collect in pockets of lymphoid tissue in a sheep's nictitating membrane, or third eyelid.