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count·er·cur·rent mech·a·nism(kownt'ĕr-kŭr'ĕnt mek'ă-nizm)
A system in the renal medulla that facilitates concentration of the urine as it passes through the renal tubules.
A mechanism used by the kidneys, making it possible to excrete excess solutes in the urine with little loss of water from the body.
See also: mechanism