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The Body Fluids and Kidneys Lecture 14 Urine Formation II Regulation of Tubular Reabsorption

The Body Fluids and Kidneys Lecture 14 Urine Formation II Regulation of Tubular Reabsorption. Regulation of Tubular Reabsorption. Reabsorption= 124 ml/min. Reabsorption= K f × Net Reabsorptive Force K f = Capillary Co-Efficient = Permeability × Surface Area.

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The Body Fluids and Kidneys Lecture 14 Urine Formation II Regulation of Tubular Reabsorption

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  1. The Body Fluids and Kidneys Lecture 14 Urine Formation II Regulation of Tubular Reabsorption

  2. Regulation of Tubular Reabsorption

  3. Reabsorption=124 ml/min Reabsorption= Kf× Net Reabsorptive Force Kf = Capillary Co-Efficient = Permeability × Surface Area

  4. Reabsorptive Force

  5. Regulation of Peritubular Capillary Physical Forces • Arterial Pressure: ↑ BP : ↓ Reabsorption ( ↑ Pc ) 2. Resistance of Afferent & Efferent Arterioles: ↑ Resistance: ↓ Pc : ↑ Reabsorption 3. Systemic Colloid Osmotic Pressure: ↑ πc: ↑ Reabsorption 4. Filtration Fraction: ↑πc: Reabsorption

  6. Forces that increase/decrease peritubular capillary reabsorption also increases/decreases reabsorption from renal tubules

  7. Pressure Diuresis Pressure Natriuresis • ↑ BP → ↑ GFR • ↑ BP → ↑ Pc→↓ Reabsorption • ↓ Angiotensin-II

  8. Hormonal Control of Tubular Reabsorption

  9. HORMONES THAT REGULATE ABSORPTION

  10. Angiotensin-II • ↑ Aldosterone • Constriction of Efferent Arterioles i. ↓Pc → ↑ Reabsorption ii. ↓ Renal Blood Flow → ↑ Filtration Fraction → ↑ πc → ↑ Reabsorption • Direct stimulation of Sodium Reabsorption • Stimulation of Na+,K+ ATPase • Stimulation of Na+,H+ Counter-transport • Sodium bicarbonate co transport

  11. ↑ADH Effect of Angiotensin-II on Na+ and Water Reabsorption OVLT→Hypothalamus Angiotensin-II ↑ thirst Constriction of efferent arterioles ↑ Aldosterone Direct stimulation of Sodium Reabsorption ↓Pc ↓Renal Blood Flow Stimulation of Na+,K+ ATPase ↑ Filtration Fraction Stimulation of Na+,H+ Counter-transport ↑πc ↑ Reabsorption ↑ Na+ Reabsorption

  12. ↑ADH Effect of Angiotensin-II on Na+ and Water Reabsorption OVLT→Hypothalamus Angiotensin-II ↑ thirst Constriction of efferent arterioles ↑ Aldosterone Direct stimulation of Sodium Reabsorption ↓Pc ↓Renal Blood Flow Stimulation of Na+,K+ ATPase ↑ Filtration Fraction Stimulation of Na+,H+ Cotransport ↑πc ↑ Reabsorption ↑ Na+ Reabsorption

  13. HORMONES THAT REGULATE ABSORPTION

  14. Anti-diuretic hormone • Site of action • Late distal tubules, collecting tubules, collecting ducts • Binds to specific V2 receptors → movement of an intracellular protein, AQP-2 (Aquaporin-2) to luminal side of cell→ molecules of AQP-2 fuse with cell membrane by exocytosis → water channels →↑ water permeability

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