Callus (redirected from external callus)
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corns and calluses
corns and calluses,
thickenings of the outer layer of skin
where there is irritation or constant pressure. Corns are cone-shaped with their points protruding into the dermis, or inner layer of skin. They usually have hard, shiny surfaces surrounded by red, painful areas. Soft-surfaced corns sometimes develop between overlapping toes where there is an accumulation of moisture. Treatment of corns is directed at the relief of irritation or pressure, e.g., wearing properly fitted shoes; they can also be softened by pastes and ointments or removed by a physician. Calluses typically involve only the outermost layers of skin and are not usually painful; they tend to disappear once the source of irritation has been removed. See bunion
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
(1) Tissue formed in plants on the surface of a wound (cracks, taps, the bases of cuttings, and areas of concrescence of stock and scion). A callus promotes the healing of wounds. Consisting of thin-walled parenchymal cells, a callus develops when there is cell division of any living tissue of the plant (cambium or phloem) in the peripheral zone of the pith, lying next to the protoxylem. Adventitious roots and buds, particularly with grafting, often develop in the callus. (2) Corpus callosum, an accumulation of callóse that obstructs the sieve plate when the sieve tubes of the phloem age. Use of the term in this sense is obsolete.
a thickening of the horny layer of skin as a result of constant pressure or friction. Calluses usually appear on the palms, soles, and other parts of the body that are in constant contact with tough surfaces. The cracks formed on the surface of a callus may hinder one’s ability to work, and they can also be portals of entry for pyogenic microbes, resulting in such conditions as erysipelatous inflammations and phlegmons.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
A thickened callose deposit on sieve plates.
A hard tissue that forms over a damaged plant surface.
Hard, thick area on the surface of the skin.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
1. an area of skin that is hard or thick, esp on the palm of the hand or sole of the foot, as from continual friction or pressure
2. an area of bony tissue formed during the healing of a fractured bone
a. a mass of hard protective tissue produced in woody plants at the site of an injury
b. an accumulation of callose in the sieve tubes
4. Biotechnology a mass of undifferentiated cells produced as the first stage in tissue culture
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005