1. Aggregates of atoms or molecules in a finely divided state (submicroscopic), dispersed in a gaseous, liquid, or solid medium, and resisting sedimentation, diffusion, and filtration, thus differing from precipitates. SEE ALSO: hydrocolloid. 2. Gluelike. 3. A translucent, yellowish, homogeneous material of the consistency of glue, less fluid than mucoid or mucinoid, found in the cells and tissues in a state of c. degeneration. SYN: colloidin. 4. The stored secretion within follicles of the thyroid gland. For individual colloids not listed below, see the specific name. [G. kolla, glue, + eidos, appearance]
- bovine c. SYN: conglutinin.
- emulsion c. SYN: emulsoid.
- hydrophil c., hydrophilic c. SYN: emulsoid.
- irreversible c. a c. that is not again soluble in water after having been dried at ordinary temperature. SYN: unstable c..
- lyophilic c. SYN: emulsoid.
- protective c. a c. that has the power of preventing the precipitation of suspensoids under the influence of an electrolyte.
- c. pseudomilium SYN: c. milium.
- reversible c. a c. that is again soluble in water after having been dried at ordinary temperature. SYN: stable c..
- stable c. SYN: reversible c..
- styptic c. SYN: styptic collodion.
- thyroid c. the semifluid material that occupies the lumen of thyroid follicles; it mainly contains thyroglobulin.
- unstable c. SYN: irreversible c..

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col·loid 'käl-.ȯid n
1) a gelatinous or mucinous substance found in tissues in disease or normally (as in the thyroid)
2 a) a substance consisting of particles that are dispersed throughout another substance and are too small for resolution with an ordinary light microscope but are incapable of passing through a semipermeable membrane
b) a mixture (as smoke) consisting of a colloid together with the medium in which it is dispersed
col·loi·dal kə-'lȯid-əl, kä- adj
col·loi·dal·ly -əl-ē adv

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col·loid (kolґoid) [Gr. kollōdēs glutinous] 1. glutinous or resembling glue. 2. a substance comprising very small, insoluble particles, usually 1 to 1000 nm in diameter, that are uniformly dispersed or suspended in a finely divided state throughout a continuous dispersion medium, not settling readily; the phase may be solid, liquid, or gas. The particles are often called the dispersed phase and the dispersion medium the continuous phase. Colloid can refer specifically to the particles or to the system of particles plus dispersion medium. 3. thyroid c. colloidal adj

Medical dictionary. 2011.

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