tapetum lucidum


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tapetum

 [tah-pe´tum] (L.)
1. a covering structure or layer of cells.
2. a stratum in the human brain composed of fibers from the body and splenium of the corpus callosum sweeping around the lateral ventricle.
tapetum lu´cidum the iridescent epithelium of the choroid of animals that gives their eyes the property of shining in the dark.

tapetum lucidum

A layer of tissue in the choroid of the eye between the vascular and capillary layers in some animals, but not in humans. This membrane reflects light shined into the animal's eyes. It produces a green reflection, readily seen in cats.
Synonym: tapetum choroideae
See also: tapetum

tapetum lucidum 

A reflecting pigment layer lying behind the visual receptors of the retina of certain mammals (e.g. cats, dogs), birds and fish, which gives a shining appearance to the eyes when illuminated in the dark. The tapetum is located either in the pigment epithelium or in the choroid and covers either the whole fundus or more often only the upper and back portion. The role of the tapetum lucidum is to increase the probability of visual stimulation of the photoreceptors by reflecting light back after having already traversed them once, thus aiding vision in dim illumination. In some species the tapetum consists of guanine crystals.

tapetum

pl. tapeta [L.]
1. a covering structure or layer of cells.
2. a stratum in the human brain composed of fibers from the body and splenium of the corpus callosum sweeping around the lateral ventricle.

tapetum cellulosum
a type of tapetum lucidum made of cells called iridocytes, as found in carnivores.
choroidal tapetum
see tapetum lucidum (below).
tapetum fibrosum
a type of tapetum lucidum composed predominantly of organized bundles of collagen as found in ungulates.
tapetum lucidum
the iridescent reflecting tissue layer of the choroid of some species of animals that gives their eyes the property of shining in the dark. It is characteristic of nocturnal animals and allows incident light two opportunities to stimulate the retinal receptors. Called also choroidal tapetum.
References in periodicals archive ?
2008) observed absence of tapetum lucidum at birth in dog as its development started at age 37 days and underwent color and consistence modifications until 90 days of life.
After passing through the retina, they are reflected by the tapetum lucidum and have a second chance of stimulating a photoreceptor cell.
Thanks to the tapetum lucidum, a cat's sensitivity to light is thought to be about six times greater than that of a human's.
After passing through the retina they are reflected by the tapetum lucidum and have a second chance of stimulating a photoreceptor cell.