Countercurrent multiplication

A countercurrent mechanism system is a mechanism that expends energy to create a concentration gradient. A countercurrent mechanism system is a mechanism that expends energy to create a concentration gradient. It is found widely in nature and especially in mammalian organs. For example, it can refer to the process that is underlying the process of urine concentration, that is, the production of hyperosmotic urine by the mammalian kidney.The ability to concentrate urine is also present in birds. Countercurrent multiplication is frequently mistaken for countercurrent exchange, a similar but different mechanism where gradients are maintained, but not established. The term derives from the form and function of the loop of Henle, which consists of two parallel limbs of renal tubules running in opposite directions, separated by the interstitial space of the renal medulla. Countercurrent multiplication was originally studied as a mechanism whereby urine is concentrated in the nephron. Initially studied in the 1950s by Gottschalk and Mylle following Werner Kuhn's postulations, this mechanism gained popularity only after a series of complicated micropuncture experiments.