nictitating membrane


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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

nictitating membrane

(nĭk′tĭ-tā′tĭng)
n.
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.
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].
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.
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.
Key words: Oxyspirura mansoni, detection, nictitating membrane, cock.
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.
And a nictitating membrane protects its beady eyes from flying dirt.
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.
The nictitating membrane of large animals is frequently affected by neoplasms, malformations, foreign bodies and inflammations (Hendrix, 2007).
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.
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).
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.
Their eyes are protected by a nictitating membrane that moves up and down like an eyelid.