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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. All Anura [1] (tailless amphibians), and some reptiles, birds, and sharks have full nictitating membranes; in ...
The scleral ring is a hardened ring of plates, often derived from bone, that is found in the eyes of many animals in several groups of vertebrates. Some species of mammals, amphibians, and crocodilians lack scleral rings. [ 1] The ring is in the fibrous outer layer of the eye, called the sclera. The structure is commonly referred to as the ...
Anurans. In frogs and toads, the tympanum is a large external oval shape membrane made up of nonglandular skin. [ 2] It is located just behind the eye. It does not process sound waves; it simply transmits them to the inner parts of the amphibian's ear, which is protected from the entry of water and other foreign objects.
The tapetum lucidum ( Latin for 'bright tapestry, coverlet'; / təˈpiːtəm ˈluːsɪdəm / tə-PEE-təm LOO-sih-dəm; pl.: tapeta lucida) [ 1] is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina, it is a retroreflector. It reflects visible light back through the retina, increasing ...
Anatomy of the avian eye. The main structures of the bird eye are similar to those of other vertebrates.The outer layer of the eye consists of the transparent cornea at the front, and two layers of sclera — a tough white collagen fibre layer which surrounds the rest of the eye and supports and protects the eye as a whole.
A parietal eye ( third eye, pineal eye) is a part of the epithalamus in some vertebrates. The eye is at the top of the head; is photoreceptive; and is associated with the pineal gland, which regulates circadian rhythmicity and hormone production for thermoregulation. [ 1] The hole that contains the eye is known as the pineal foramen or parietal ...
Vision in toads. The eye of a toad. The neural basis of prey detection, recognition, and orientation was studied in depth by Jörg-Peter Ewert in a series of experiments that made the toad visual system a model system in neuroethology (neural basis of natural behavior). He began by observing the natural prey catching behavior of the common ...
Vitelline membrane. The vitelline membrane or vitelline envelope is a structure surrounding the outer surface of the plasma membrane of an ovum (the oolemma) or, in some animals (e.g., birds), the extracellular yolk and the oolemma. It is composed mostly of protein fibers, with protein receptors needed for sperm binding which, in turn, are ...