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.

nictitating membrane

see also membrana nictitans, third eyelid.

nictitating membrane flap
using the membrana nictitans (third eyelid) as a flap in the treatment of corneal ulcer by sewing the eyelid across the cornea.
nictitating membrane prolapse
occurs when the globe of the eye is depressed in the orbit, as in dehydration and emaciation. It is also a diagnostic sign of tetanus in many species; the membrane flicks across the eye whenever the animal is startled.
References in periodicals archive ?
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.
1974) demonstrated that the surgical removal of nictitating membrane gland resulted in 29-57% reduction of Schirmer tear test values.
Every effort was made to directly contact the cornea to obtain measurements, and this proved time consuming because of the constant "flashing" of the nictitating membrane in all birds and with both devices.
And sharks have a nictitating membrane that protects their eyes while they feed.
The conjunctival incision was sutured over nictitating membrane using silk no.
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.
7) Only 2 glands constitute the avian lacrimal apparatus: the gland of the nictitating membrane (formerly Harders gland) and the lacrimal gland.
Keratoconjunctivitis sicca: histopathologic study of nictitating membrane and lacrimal gland from 28 dogs.
Dermoid is a congenital defect in which skin containing hair follicles is found in cornea alone, conjunctiva (palpebral and bulbar) and nictitating membrane (Helper, 1989).
The mobility of the nictitating membrane was impaired because of the presence of the plaque over the cornea.
A male Labrador dog, 7 years of age was brought with a complaint of prolapsed nictitating membrane of right eye.