cell theory

theory /the·o·ry/ (the´o-re)

1. the doctrine or the principles underlying an art as distinguished from the practice of that particular art.

2. a formulated hypothesis or, loosely speaking, any hypothesis or opinion not based upon actual knowledge.

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cell theory  all organic matter consists of cells, and cell activity is the essential process of life.

clonal deletion theory  a theory of immunologic self-tolerance according to which “forbidden clones” of immunocytes, those reactive with self antigens, are eliminated on contact with antigen during fetal life.

clonal selection theory  there are several million clones of antibody-producing cells in each adult, each programmed to make an antibody of a single specificity and carrying cell-surface receptors for specific antigens; exposure to antigen induces cells with receptors for that antigen to proliferate and produce large quantities of specific antibody.

information theory  a system for analyzing, chiefly by statistical methods, the characteristics of communicated messages and the systems that encode, transmit, distort, receive, and decode them.

overflow theory  one similar to the underfilling theory but which proposes that the primary event in ascites formation is sodium and water retention with portal hypertension resulting; plasma volume expansion to the point of overflow from the hepatic sinusoids then causes ascites formation.

quantum theory  radiation and absorption of energy occur in quantities (quanta) which vary in size with the frequency of the radiation.

recapitulation theory  ontogeny recapitulates phylogeny, i.e., an organism in the course of its development goes through the same successive stages (in abbreviated form) as did the species in its evolutionary development.

underfilling theory  a theory that ascites associated with portal hypertension causes hypovolemia and so both a lowering of portal pressure and retention of sodium and water. The higher sodium concentration causes increases in the plasma volume and portal pressure, and the subsequent formation of ascites renews the cycle.

Young-Helmholtz theory  color vision depends on three sets of retinal receptors, corresponding to the colors red, green, and violet.

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cell theory,

the proposition that cells are the basic units of all living tissues or organisms and that cellular function is the essential process of living things.

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theory

1. the doctrine or the principles underlying an art as distinguished from the practice of that particular art.

2. a formulated hypothesis or, loosely speaking, any hypothesis or opinion not based upon actual knowledge.

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cell theory

all organic matter consists of cells, and cell activity is the essential process of life.

recapitulation theory

see recapitulation theory.