Search results
Results from the WOW.Com Content Network
The nictitating membrane of a masked lapwing as it closes over the left eye, originating from the medial canthus. The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision.
It is loose, thus eye movements are not restricted by it. Only one species of primate, the Calabar angwantibo, is known to have a functioning nictitating membrane. [4] With ocular allergies, the lacrimal caruncle and plica semilunaris may be inflamed and pruritic (itchy) due to histamine release in the tissue and tear film.
The Harderian gland is a gland found within the eye's orbit that occurs in tetrapods (reptiles, amphibians, birds and mammals) that possess a nictitating membrane. [1] The gland can be compound tubular or compound tubuloalveolar, and the fluid it secretes (mucous, serous or lipid) varies between different groups of animals.
The eyelids of a bird are not used in blinking. Instead the eye is lubricated by the nictitating membrane, a third concealed eyelid that sweeps horizontally across the eye like a windscreen wiper. [12] The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds when they are under water. [5]
Naïve organisms initially produce a reflexive, unconditioned response (UR) (e.g. blink or extension of nictitating membrane) that follows US onset. After many CS-US pairings, an association is formed such that a learned blink, or conditioned response (CR), occurs and precedes US onset. [ 1 ]
This is a very valuable sequence; the timing is impressive, and the result is a world of difference from the other images in commons:Category:Nictitating membrane. Obviously cropping this tightly results in a considerable sacrifice of resolution and there may be other tiny (but understandable) technical issues, but on balance those things are ...
In squamate reptiles both the nictitating membrane and the eyelids have been suggested as the evolutionary origin of the brille, but embryonic studies supports the fusion of the dorsal and ventral eyelids. [1] Brille means "spectacles" or "glasses" in German, Norwegian, and Danish.
Ileum, caecum and colon of rabbit, showing Appendix vermiformis on fully functional caecum The human vermiform appendix on the vestigial caecum. The appendix was once believed to be a vestige of a redundant organ that in ancestral species had digestive functions, much as it still does in extant species in which intestinal flora hydrolyze cellulose and similar indigestible plant materials. [10]