tapetum lucidum

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.

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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.

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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.