The Loop of Henle

• The Loops of Henle collectively concentrate salts in the tissue fluid of the medulla. This causes an osmotic flow of water out of the collecting ducts which concentrates urine.
• The Loop of Henle (along with the capillaries of the vasa recta and collecting duct) maintains an osmotic gradient in the medulla
• Describe how the ascending limb of the Loop of Henle works.?

  -impermeable to water

  -so water cannot move out of the filtrate

  -Na+ and Cl- are actively pumped out of the filtrate into the tissue fluid

  SO

  • water flows out of the descending limb by osmosis
  • Na+ and Cl- diffuse down a concentration gradient
• Describe how the descending limb of the Loop of Henle works.?

  -highly permeable to water and most solutes

  -filtrate becomes increasingly concentrated as it passes down, because water moves out by osmosis and urea moves in by active transport

  -when fluid reaches the bottom of the descending limb, it is very concentrated due to the accumulation of Na+ and Cl-

  -as the fluid goes up the ascending limb, it gets more and more dilute as Na+ and Cl- are actively pumped out