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FORMATION OF DILUTE URINE & COUNTER CURRENT MECHANISM

FORMATION OF DILUTE URINE & COUNTER CURRENT MECHANISM. Total body water is controlled by: 1. Fluid Intake: a. Thirst b. Salt appetite 2. Renal excretion of water and solutes. FORMATION OF DILUTE URINE. ADH mechanism Renal excretion of dilute urine.

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FORMATION OF DILUTE URINE & COUNTER CURRENT MECHANISM

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  1. FORMATION OF DILUTE URINE & COUNTER CURRENT MECHANISM

  2. Total body water is controlled by: 1. Fluid Intake: a. Thirst b. Salt appetite 2. Renal excretion of water and solutes

  3. FORMATION OF DILUTE URINE • ADH mechanism • Renal excretion of dilute urine

  4. ADH hormone controls hormone conc. • ADH stimulated by  osmolarity • ADH inhibited by  Osmolarity • ADH present; 99% water Is obsorbed • ADH absent ; 88% water is absorbed

  5. Renal mechanisms for excreting a dilute urine

  6. Counter-Current Mechanism Renal concentration of urine

  7. Independent regulation of water excretion: Counter-current mechanism

  8. Counter-Current Mechanism • Counter = opposite • Current = flow • Definition: • A counter-current system is a system in which the inflow runs parallel to the outflow for some distance. • Loop of Henle • Vasa recta

  9. Requirements for excreting concentrated urine • High ADH level • Hyperosmotic renal medulla • Produced by COUNTERCURRENT multipliers • Active transport of ions • Relatively less absorption of water • Urea and NaCl trapping • Maintained by COUNTERCURRENT exchangers

  10. Components 6 Medullary Interstitium 4 5a 1 to 5 Nephron Counter- Current Multipliers 3 7 Vasa Recta Counter- Current Exchangers 5b 6 1 5c 2 7

  11. Fundamental Processes • Active Transport of Na+ and co-transport of K+ and Cl- out of thick ALH • Passive diffusion of Urea from inner medullary collecting duct • Passive absorption of relatively large amounts of water

  12. Permeability of different segments of nephron

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