| countercurrent | 1. Flowing in an opposite direction. 2. A current flowing in a direction opposite to another current. (05 Mar 2000) |
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| countercurrent distribution | A method of separation of two or more substances by repeated distribution between two immiscible liquid phases that move past each other in opposite directions. It is a form of liquid-liquid chromatography. (12 Dec 1998) |
| countercurrent exchanger | A system in which heat or chemicals passively diffuse across a membrane separating two countercurrent exchanger streams so that at each end the fluid leaving along one side of the membrane nearly resembles, in temperature or composition, the fluid entering the other; e.g., the venae comites in the arms serve as a countercurrent exchanger exchanger, the arterial blood serving to rewarm the cooler venous blood. (05 Mar 2000) |
| countercurrent mechanism | A system in the renal medulla that facilitates concentration of the urine as it passes through the renal tubules. See: countercurrent exchanger, countercurrent multiplier. (05 Mar 2000) |
| countercurrent multiplier | A system in which energy is used to transport material across a membrane separating two countercurrent multiplier tubes connected at one end to form a hairpin shape; by this means a concentration can be achieved in the fluid in the hairpin bend, relative to the inflow and outflow fluids, that is much greater than the transport mechanism could produce between the two sides of the membrane at any point; e.g., the nephronic loops in the renal medulla act as countercurrent multipliers. (05 Mar 2000) |