pli·ca sem·i·lu·na·'ris of con·junc·ti·'va

[TA]

1. the semilunar fold formed by the palpebral conjunctiva at the medial angle of the eye;

2. a fold of the conjunctival mucous membrane found in many animals; normally partially hidden in the medial canthus of the eye when at rest, it may be extended to cover part or all of the cornea in a winklike action to clean the cornea, as in birds. Synonym(s): membrana nictitans, nictitating membrane, palpebra III, palpebra tertia, third eyelid

Synonym(s): plica semilunaris conjunctivae [TA], plica lunata, plica semilunaris of eye, semilunar conjunctival fold

Farlex Partner Medical Dictionary © Farlex 2012

nictitating membrane

(nĭk′tĭ-tā′tĭng)

A transparent inner eyelid in many vertebrates that closes to protect and moisten the eye. Also called third eyelid.

nictitating membrane

the third eyelid that occurs in birds, reptiles, and some mammals, sharks and amphibians. It is transparent and flicks over the eyeball from the inner (anterior) corner of the eye to clean and moisten the eyeball without shutting out the light. In some diving birds such as auks, there is a lens-like window in the membrane which adjusts the focus of the eye under water.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

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References in periodicals archive

Although the majority of the research into learning in rabbits is based on changes in skeletal responses, particularly the closure of the upper eyelid and the sweep of the nictitating membrane [35], a significant body of research has examined an autonomic response--deceleration of heart rate [73-80].

Cholesterol and copper affect learning and memory in the rabbit

Horny or scaly skin may be related to the nictitating membrane. Another source Rashi utilizes is TB Sotah 14a (found also in the Zohar, 1:36b), where we find that or is understood as something derived from skin or soothing to the skin.

Kotnot or (Genesis 3:21): skin, leather, light, or blind?

Cats in groups 1 and 2 infected with pandemic (H1N1) 2009 virus showed mild-to-moderate clinical signs (lethargy, appetite loss, rapid and labored breathing, and protruding nictitating membrane) after 1 dpi or 2 dpi onwards.

Experimental pandemic (H1N1) 2009 virus infection of cats

Key words: Oxyspirura mansoni, detection, nictitating membrane, cock.

Oxyspirura mansoni (Spirurida: thelaziidae) en gallos de pelea del estado trujillo. Nota tecnica

These currents are thought to be responsible for the enhanced long-lasting depolarization (LLD) exhibited in Hermissenda photoreceptors when these animals are exposed to Pavlovian conditioning, and for the increased EPSP summation seen in the vertebrate hippocampus after nictitating membrane conditioning.

Lead, learning, and calexcitin in Hermissenda

And a nictitating membrane protects its beady eyes from flying dirt.

The benefits of badgers

In addition, certain benign stimuli were applied to assess pupillary, corneal (blink and nictitating membrane), defense (reacting to approach with attempts to withdraw or bite), skin sensitivity, pedal, tail, and audio responses.

Crocodilian slaughter methods, with special reference to spinal cord severance

The nictitating membrane of large animals is frequently affected by neoplasms, malformations, foreign bodies and inflammations (Hendrix, 2007).

A Retrospective Study on Ocular Affections in Bovines

Corneal sensitivity was considered present if the bird blinked its eyelids or flashed the nictitating membrane when the cotton wisp was applied; it was considered absent if no such response was observed, and diminished if the response was less robust than in cohort birds.

Ophthalmic diagnostic tests and ocular findings in a flock of captive American flamingos (Phoenicopterus ruber ruber)

In other birds, chondrosarcomas have been described in the metatarsophalangeal joint (SIEGFRIED, 1983), nictitating membrane (SPALDING & WOODARD, 1992), tarsal bones (KENNEDY et al., 1995), carpus (KUBO et al., 2007), sternum (DITTMER et al., 2012), and ventriculus (ERDOGAN et al., 2013).

Vertebral chondrosarcoma in a blue-fronted parrot (Amazona aestiva)/Condrossarcoma vertebral em papagaio (Amazona aestiva)

Next, you should check your cat's eyes to ensure that the pupils are the same size, that there is no tearing or discharge, and that the third eyelid (nictitating membrane) isn't drawn over the eye.

A health checklist to perform at home; nothing replaces regular veterinary visits to keep your cat in optimum health. But you should be part of the team, too

Their eyes are protected by a nictitating membrane that moves up and down like an eyelid.

What do you know about SHARKS?