Friday, March 11, 2016

Plica Semilunaris

The Plica Semilunaris is a small fold of bulbar conjunctiva on the medial canthus of the eye. It functions during movement of the eye, to help maintain tear drainage via the lacrimal lake, and to permit greater rotation of the globe; without the plica the conjunctiva would attach directly to the eyeball, restricting movement.

It is the vestigial remnant of the nictitating membrane (the "third eyelid") which is drawn across the eye for protection, and is present in other "creatures" such as birds, reptiles, and fish, but is rare in mammals, mainly found in monotremes and marsupials.
Know your eyes:

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