The loop of Henlé is responsible for the reabsorption of water. 125cm3 per minute of fluid is filtered into the kidneys and about 106cm3 (about 85%) is reabsorbed by the proximal CT. Fluid descends into the medulla through the descending limb of the loop of Henle and ascends back out to the cortex in the ascending limb. The ascending limb is impermeable to water. As the fluid descends a counter current multiplier system results in water moving from the fluid to the surrounding interstitial fluid in the medulla by osmosis.