cones

conetop: right circular conebottom: cones and rods of a human eye

cone

C0556800 (kōn)n.1. Mathematics a. The surface generated by a straight line, the generator, passing through a fixed point, the vertex, and moving along a fixed curve, the directrix.b. A right circular cone.2. a. The figure formed by a cone, bound or regarded as bound by its vertex and a plane section taken anywhere above or below the vertex.b. Something having the shape of this figure: "the cone of illuminated drops spilling beneath a street lamp" (Anne Tyler).3. Botany a. A unisexual reproductive structure of most gymnospermous plants, such as conifers and cycads, typically consisting of a central axis around which there are scaly, overlapping, spirally arranged sporophylls that bear either pollen-containing structures or ovules.b. A similar, spore-producing structure of club mosses, horsetails, and spikemosses.c. A reproductive structure resembling a cone, such as the female inflorescence of a hop plant or the woody female catkin of an alder.4. Physiology One of the photoreceptors in the retina of the eye that is responsible for daylight and color vision. These photoreceptors are most densely concentrated in the fovea centralis, creating the area of greatest visual acuity. Also called cone cell.5. Any of various gastropod mollusks of the family Conidae of tropical and subtropical seas that have a conical, often vividly marked shell and that inject their prey with poisonous toxins, which can be fatal to humans. Also called cone shell.tr.v. coned, con·ing, cones To shape (something) like a cone or a segment of one.

[French cône and Middle English cone, angle of a quadrant, both from Latin cōnus, from Greek kōnos; see kō- in Indo-European roots.]

cones

Receptor cells in the retina. They sense bright light and function in daylight. See retina.

Cones

in man and vertebrates, cone-shaped photoreceptors of the eye that function in the perception of daylight and provide color vision. They are located, together with the rods, in the outer layer of the retina.

The cones are made up of an external segment, an internal segment, a connective fiber, a nucleus-containing portion, and an internal fiber that ends in a thickening in which a synaptic juncture is established with the bipolar and horizontal nerve cells of the retina. The ultrastructure of the cone indicates that the external segment is a derivative of cilia. It is constructed of numerous membranous disks containing visual pigment. The internal segment contains mitochondria and a fat drop. In many vertebrates the internal segment also contains a contractile element called the myoid. The external and internal segments are joined by a delicate structure that consists of nine pairs of double threads distributed along the periphery; the central pair of threads, characteristic of movable cilia, is absent.

Cones predominate over rods in the retinas of diurnal animals (for example, the suslik has only rods). In man, cones predominate at the center of the retina and rods predominate along the edges. The central depression, or fovea, contains only cones.

O. G. STROEVA

cones

The tiny light-sensitive transducers of the RETINA that are present in greatest concentration in the central part, the macula. Cones are less sensitive than the more peripherally placed, colour-blind rods, but are capable of distinguishing three primary colours.

Cones

Receptor cells that allow the perception of colors.Mentioned in: Color Blindness

单词	cones
释义	cones conetop: right circular conebottom: cones and rods of a human eye cone C0556800 (kōn)n.1. Mathematics a. The surface generated by a straight line, the generator, passing through a fixed point, the vertex, and moving along a fixed curve, the directrix.b. A right circular cone.2. a. The figure formed by a cone, bound or regarded as bound by its vertex and a plane section taken anywhere above or below the vertex.b. Something having the shape of this figure: "the cone of illuminated drops spilling beneath a street lamp" (Anne Tyler).3. Botany a. A unisexual reproductive structure of most gymnospermous plants, such as conifers and cycads, typically consisting of a central axis around which there are scaly, overlapping, spirally arranged sporophylls that bear either pollen-containing structures or ovules.b. A similar, spore-producing structure of club mosses, horsetails, and spikemosses.c. A reproductive structure resembling a cone, such as the female inflorescence of a hop plant or the woody female catkin of an alder.4. Physiology One of the photoreceptors in the retina of the eye that is responsible for daylight and color vision. These photoreceptors are most densely concentrated in the fovea centralis, creating the area of greatest visual acuity. Also called cone cell.5. Any of various gastropod mollusks of the family Conidae of tropical and subtropical seas that have a conical, often vividly marked shell and that inject their prey with poisonous toxins, which can be fatal to humans. Also called cone shell.tr.v. coned, con·ing, cones To shape (something) like a cone or a segment of one. [French cône and Middle English cone, angle of a quadrant, both from Latin cōnus, from Greek kōnos; see kō- in Indo-European roots.] cones Receptor cells in the retina. They sense bright light and function in daylight. See retina. cones cones n. the breasts; female breasts. She ain’t much in the cones department. See also: cone Cones Cones in man and vertebrates, cone-shaped photoreceptors of the eye that function in the perception of daylight and provide color vision. They are located, together with the rods, in the outer layer of the retina. The cones are made up of an external segment, an internal segment, a connective fiber, a nucleus-containing portion, and an internal fiber that ends in a thickening in which a synaptic juncture is established with the bipolar and horizontal nerve cells of the retina. The ultrastructure of the cone indicates that the external segment is a derivative of cilia. It is constructed of numerous membranous disks containing visual pigment. The internal segment contains mitochondria and a fat drop. In many vertebrates the internal segment also contains a contractile element called the myoid. The external and internal segments are joined by a delicate structure that consists of nine pairs of double threads distributed along the periphery; the central pair of threads, characteristic of movable cilia, is absent. Cones predominate over rods in the retinas of diurnal animals (for example, the suslik has only rods). In man, cones predominate at the center of the retina and rods predominate along the edges. The central depression, or fovea, contains only cones. O. G. STROEVA cones cones The tiny light-sensitive transducers of the RETINA that are present in greatest concentration in the central part, the macula. Cones are less sensitive than the more peripherally placed, colour-blind rods, but are capable of distinguishing three primary colours. Cones Receptor cells that allow the perception of colors.Mentioned in: Color Blindness ThesaurusSeecone
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