| osmotic pressure | See: osmosis. The pressure required to prevent osmotic flow across a semi permeable membrane separating two solutions of different solute concentration. Equal to the pressure that can be set up by osmotic flow in this system. (18 Nov 1997) |
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| effective osmotic pressure | That part of the total osmotic pressure of a solution that governs the tendency of its solvent to pass across a boundary, usually a semipermeable membrane; it is commonly represented by the product of the total osmotic pressure of the solution and the ratio (corrected for activities) of the number of dissolved particles that do not permeate the bounding membrane to the total number of particles in the solution; equivalent in meaning to tonicity; commonly expressed in equivalent units of osmolality rather than pressure per se. (05 Mar 2000) |
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| diuretics, osmotic | Diuretics that are filtered at the glomerulus and reabsorbed in the renal tubule only to a limited extent. They thus increase the amount of osmotically active solute in the urine and a corresponding increase in urine volume. These compounds also increase the osmolality of plasma, thereby increasing the diffusion of water from the intraocular and cerebrospinal fluids; they can be used for reducing the pressure and volume of these fluids. (12 Dec 1998) |
| iso-osmotic | <physiology> Having the same total osmotic pressure or osmolality as another fluid (ordinarily intracellular fluid); such a fluid is not isosmotic if it includes solutes that freely permeate cell membranes. Synonym: iso-osmotic. (05 Mar 2000) |
| osmotic | <chemistry> Pertaining to or of the nature of osmosis (= the passage of pure solvent from a solution of lesser to one of greater solute concentration when the two solutions are separated by a membrane which selectively prevents the passage of solute molecules, but is permeable to the solvent). (18 Nov 1997) |
| osmotic diuresis | Diuresis due to a high concentration of osmotically active substances in the renal tubules (e.g., urea, sodium sulfate), which limit the reabsorption of water. (05 Mar 2000) |
| osmotic diuretics | Drugs, such as mannitol, which by their osmotic effects retain water during urine formation and thus dilute electrolytes in the urine, making resorption less efficient; they promote the elimination of water and electrolytes in the urine. (05 Mar 2000) |
| osmotic fragility | The susceptibility, or lack of resistance, of erythrocytes to haemolysis when exposed to increasingly hypotonic saline solutions. (12 Dec 1998) |
| osmotic nephrosis | Swelling of renal tubular epithelium associated with glomerular filtration of sugars and dextrose; the swelling is due to formation of cytoplasmic vesicles by pinocytosis, and is reversible, probably with no dysfunction, when produced by glucose or mannitol. (05 Mar 2000) |
| osmotic shock | Passage of solvent into a membrane bound structure due to osmosis, causing rupture of the membrane. A method of lysing cells or organelles. (18 Nov 1997) |
| abdominal pressure | Pressure surrounding the bladder; estimated from rectal, gastric, or intraperitoneal pressure. (05 Mar 2000) |
| absolute pressure | Pressure measured with respect to zero pressure. Compare: gauge pressure. (05 Mar 2000) |
| acoustic pressure | In ultrasound, the instantaneous value of the total pressure minus the ambient pressure; unit is pascal (Pa). (05 Mar 2000) |
| air pressure | The force per unit area that the air exerts on any surface in contact with it. Primarily used for articles pertaining to air pressure within a closed environment. (12 Dec 1998) |
| atmospheric pressure | The pressure at any point in an atmosphere due solely to the weight of the atmospheric gases above the point concerned. (12 Dec 1998) |
| back pressure | Pressure exerted upstream in the circulation as a result of obstruction to forward flow, as when congestion in the pulmonary circulation results from stenosis of the mitral valve or failure of the left ventricle. (05 Mar 2000) |