Descending limb

Lucien Rizzo

The descending loop of Henle traverses cortex/medulla. Its main function is to create a concentration gradient in the medulla. 

Receive:

  • Isotonic filtrate (~300 mOsm/L)

Process:

  • Great amount of H2O reabsorption.
  • Also some reabsorption of urea, K+, Na+, Cl-, Glucose, amino acids, lactate, phosphate, HCO3-

Produce:

  • Water is much more permeable than ions in the descending limb. Because of this H20 rapidly perfuses out of the lumen and the filtrate becomes hypertonic.  
  • Max tonicity is achieved at the bottom of the loop (in the medulla of the kidney).

Export:

  • Hypertonic filtrate (~1200 mOsm/L)