in Excretory Products and their Elimination (Urinary System) by

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COUNTER CURRENT MECHANISM

  1. The Henle’s loop in the kidney performs the function of osmoregulation. It shows counter current multiplier mechanism.
  2. The filtrate flows in opposite directions, i.e. in the descending (downward) limb and in the ascending (upward) limb.
  3. The descending limb is relatively impermeable to salts but permeable to water.
  4. The ascending limb is impermeable to water but permeable to salts.
  5. As the filtrate enters the ascending limb, Sodium (Na+) ions are pumped out into the surrounding tissue fluid by active transport, increasing the concentration of the tissue fluid.
  6. The filtrate in the ascending limb is hypotonic since it loses salts and retains water.
  7. Due to increase in salt concentration in the tissue fluid, water comes out of the descending limb by passive transport, the filtrate in the descending limb becomes hypertonic.
  8. In case of the absence of this mechanism, dehydration of the human body would take place in less than three minutes.
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