Plaque

(1) An semi-hardened accumulation of substances from fluids that bathe an area. Examples include dental plaque and cholesterol plaque. Minerals form dental plaque around the teeth as a result of bacterial action on food particles. Dental plaque provides an ideal environment for dental caries (cavities) to develop. To reduce the risk, plaque should be removed by daily brushing and flossing, and by regular dental cleanings. Cholesterol forms plaques on the inner walls of blood vessels and can lead to blood clot formation and stroke. The risk of these problems can be reduced by maintaining normal blood cholesterol and sometimes requires medications. (2) In dermatology, a plaque is a patch of a small area of skin that appears different than the surrounding skin and is usually raised.

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1. A patch or small differentiated area on a body surface ( e.g., skin, mucosa, or arterial endothelium) or on the cut surface of an organ such as the brain; in skin, a circumscribed, elevated, superficial, and solid area greater than 1.0 cm in diameter. 2. An area of clearing in a flat confluent growth of bacteria or tissue cells, such as is caused by the lytic action of bacteriophage in an agar plate culture of bacteria, by the cytopathic effect of certain animal viruses in a sheet of cultured tissue cells, or by antibody (hemolysin) produced by lymphocytes cultured in the presence of erythrocytes and to which complement has been added. 3. A sharply defined zone of demyelination characteristic of multiple sclerosis. 4. See dental p.. [Fr. a plate]

- atheromatous p. a well-demarcated yellow area or swelling on the intimal surface of an artery; produced by intimal lipid deposit.

- bacterial p. in dentistry, a mass of filamentous microorganisms and a large variety of smaller forms attached to the surface of a tooth that, depending on bacterial activity and environmental factors, may give rise to caries, calculus, or inflammatory changes in adjacent tissue. SYN: dental p. (2), mucous p., mucinous p..

- bacteriophage p. a clear circular zone in an otherwise confluent growth of bacteria on an agar surface resulting from bacterial lysis by bacterial viruses.

- dental p. 1. the noncalcified accumulation mainly of oral microorganisms and their products that adheres tenaciously to the teeth and is not readily dislodged; 2. SYN: bacterial p..

- Hollenhorst plaques glittering, orange-yellow, atheromatous emboli in the retinal arterioles that contain cholesterol crystals and originate in the carotid artery or great vessels.

- mucous p., mucinous p. SYN: bacterial p..

- neuritic p. SYN: senile p..

- pleural p. fibrous thickening of the parietal pleura, characteristically caused by inhalation exposure to asbestos; both microscopic and macroscopic calcification in this lesion is common.

- Randall plaques mineral concentrations on renal papillae.

- senile p. a spherical mass composed primarily of amyloid fibrils and interwoven neuronal processes, frequently, although not exclusively, observed in Alzheimer disease. SYN: neuritic p..

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plaque also placque 'plak n

1 a) a localized abnormal patch on a body part or surface and esp. on the skin <psoriatic \plaque>

b) a sticky usu. colorless film on teeth that is formed by and harbors bacteria

c) an atherosclerotic lesion

d) a histopathologic lesion of brain tissue that is characteristic of Alzheimer's disease and consists of a dense proteinaceous core composed primarily of beta-amyloid that is often surrounded and infiltrated by a cluster of degenerating axons and dendrites called also senile plaque

2) a visibly distinct and esp. a clear or opaque area in a bacterial culture produced by damage to or destruction of cells by a virus

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n.

1. a layer that forms on the surface of a tooth, principally at its neck, composed of bacteria in an organic matrix. Under certain conditions the plaque may cause gingivitis, periodontal disease, or dental caries. The purpose of oral hygiene is to remove plaque.

2. a raised patch on the skin, formed by papule enlarging or coalescing to form an area 2 cm or more across.

3. a deposit, consisting of a fatty core covered with a fibrous cap, that develops on the inner wall of an artery in atherosclerosis (see atheroma).

4. any flat and often raised patch, for example on mucous membrane, resulting from local damage.

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(plak) [Fr.] 1. any patch or flat area. 2. a superficial, solid, elevated skin lesion equal to or greater than 1.0 cm (0.5 cm according to some authorities) in diameter. Cf. papule.