third eyelid
Inner protective membrane
A third eyelid is a translucent membrane that sweeps horizontally across the eye, providing protection and moisture.
Found in birds, reptiles, amphibians, and some mammals including cats and dogs, it sits beneath the outer eyelids.
In humans, only a vestigial remnant exists as a small fold in the inner corner of the eye.
- nictitating membraneTransparent inner eyelid
- hawEquine left-turn command
- blinkRapid lid movement
- catSmall furry housepet
- reptileCold-blooded scaled vertebrate
bird · shark · deep dive · frog · eye · membrane · eye protection · translucent · protective · inner · eyelid · cornea · lubricate · amphibian · desert · swimming · dust · predator
- animal visioncornea, depth perception, eagle eye, fovea, night vision
- reptile anatomyskeleton, bones, lungs, skull, ribs
- vestigial structuresappendix, coccyx, tailbone, wisdom teeth, plantaris
- eye anatomycornea, iris, retina, pupil, lens
- eye diseasescataracts, glaucoma, conjunctivitis, uveitis, pink eye
- ungulate anatomyhooves, hoof, antlers, withers, brisket