nictitating membrane


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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 ?
Fuentes, "Nictitating membrane: classical conditioning and extinction in the albino rabbit," Science, vol.
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.
Growth of nictitating membrane was recorded in a bullock (Fig.
The nictitating membrane originated ventromedially and swept in a dorsotemporal direction, was translucent with fine diffuse vasculature, and exhibited a plica marginale with variable pigmentation.
And sharks have a nictitating membrane that protects their eyes while they feed.
O'Rourke discovered that prions collect in pockets of lymphoid tissue in a sheep's nictitating membrane, or third eyelid.
The dogs included varied in age from 2-12 months and showed clinical signs like epiphora, conjunctivitis and presence of smooth cherry like red mass at medial canthus protruding from behind the leading edge of nictitating membrane (Fig.1).
Conjunctival melanomas generally affect the nictitating membrane, the eyelids, and the bulbar and/ or palpebral conjunctiva.
When the nictitating membrane (third eyelid) is visible, it can be the first sign that the cat is not well or has an eye injury.
Protrusion of gland over the free edge of nictitating membrane is called hypertrophy, hyperplasia or adenoma and commonly termed as 'Cherry Eye' (Gelatt, 1981).