nictitating membrane

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Related to nictitating: incipient, concomitant

nictitating membrane

(in reptiles, birds, and some mammals) a thin fold of skin beneath the eyelid that can be drawn across the eye

Nictitating Membrane

 

a third eyelid, located in the inner corner of the eye in some Euselachiae (fishes) and the majority of terrestrial vertebrates. The nictitating membrane is formed from a fold of the conjunctiva and is located behind the upper and lower eyelids. In terrestrial vertebrates, a transparent nictitating membrane periodically covers the cornea to clean and moisten it. Nictitating membranes are most highly developed in reptiles and birds. Among mammals, a third eyelid is absent in Echidna and Cetacea; apes and humans have rudimentary nictitating membranes in the form of semilunar folds.

nictitating membrane

[′nik·ə‚tād·iŋ ′mem‚brān]
(vertebrate zoology)
A membrane of the inner angle of the eye or below the eyelid in many vertebrates, and capable of extending over the eyeball.
References in periodicals archive ?
Additionally, the use of the TV minimized complications in acquiring readings for birds with constantly mobile nictitating membranes.
positive IHC analysis Virus isolation ([dagger]) Tissue source 4 dpi 7 dpi 4 dpi 7 dpi Respiratory Lung 4 3 4 1 Bronchus 2 0 4 0 Trachea 0 0 4 1 Nasal turbinates 0 0 2 0 Extrarespiratory Liver 0 0 0 1 Intestine 0 0 1 1 Olfactory bulb 0 0 0 1 Brain 0 0 0 1 Spleen 0 0 1 0 Tonsil 0 0 2 0 Adrenal gland 0 0 0 2 Nictitating membrane 0 0 0 2 * Four cats were examined on each day.
Blink and nictitating membrane reflexes frequently corresponded in their responses to stimuli.
First indicators of consciousness to weaken and fail are responses to pinching of the skin of the head, followed by pupillary and reflexes of the blink and nictitating membranes.
And sharks have a nictitating membrane that protects their eyes while they feed.
4) In birds, the nictitating membrane, which lies in the dorsonasal quadrant of the conjunctival sac, is a thin membrane that moves swiftly over the surface of the cornea.
A diffuse, yellow-white plaque was present over 90%-95% of the cornea, and the nictitating membrane was unable to move normally across the surface of the globe because of the presence of the plaque.
There was no change in the blepharedema or in the mobility of the nictitating membrane.
We suggest that several previous studies may underreport prevalence and abundance because in those studies only the eye surface and nictitating membrane were examined and not eye-associated tissue, ducts, glands, or sinuses.
The nictitating membrane originated dorsomedially and swept laterally across the globe.
Ocular neoplasia in birds has been reported infrequently, and solitary tumors of the nictitating membrane even less so.
Because metaplasia of the gland of the nictitating membrane caused by hypovitaminosis A could not be excluded as a differential diagnosis, therapy with vitamin A (Vitamin A Streuli, Streuli Pharma AG, Uznach, Switzerland) was initiated at 6000 IU/kg IM once, followed by 500 IU/kg IM for 3 days and 200 IU/kg IM for another 3 days.