The descending limb is the part of the loop of Henle where filtrate travels from renal cortex tissue to renal medulla tissue. This part of the loop of Henle is very water permeable, meaning water freely exits from within the loop.
In addition to increased permeability, water is drawn out of the descending limb due to an osmotic gradient created from a higher sodium concentration in surrounding renal tissues.
The salt concentration of the medulla increases as filtrate travels further in the loop. When water exits the more proximal descending limb, solutes build in the remaining filtrate and contribute to medullary hypertonicity.
Water is absorbed from the descending loop of Henle into the surrounding renal tissues, helping to increase the loop of Henle’s medullary salt concentration.
The vasa recta describes a series of capillaries maintaining the concentration gradient of renal tissue. These capillaries do so by transporting the sodium absorbed from the ascending limb back to the descending limb.
Sodium is reabsorbed into renal tissues in the ascending loop of Henle via active transport, in a process requiring ATP use.
The ascending limb of the loop of Henle moves filtrate toward the renal cortex tissue. It is more permeable to salts and impermeable to water than the descending limb.
Na+, K+ and Cl- are actively reabsorbed by the Na+/K+/2Cl- cotransporter into the renal tissues and bloodstream surrounding the Loop of Henle.
The filtrate becomes less concentrated as it exits the loop of Henle as Na+, K+ and Cl- are actively reabsorbed into renal tissues and bloodstream.
The ascending limb of the loop of Henle is impermeable to water and leads to less concentrated filtrate through the loop.
The loop of Henle exits to the distal tubule: the last major site of absorption in the nephron.
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