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Peshawar Medical College NWFP Pakistan

URINE FORMATION. Peshawar Medical College NWFP Pakistan. Glomerular Filtrate. Plasma minus plasma proteins + protein bound substances. Definition of GFR. Quantity of Glomerular Filtrate formed each Minute in all nephrons of both kidneys. Calculation Of GFR.

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Peshawar Medical College NWFP Pakistan

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  1. kidney

  2. kidney

  3. URINE FORMATION Peshawar Medical College NWFP Pakistan

  4. Glomerular Filtrate • Plasma minus plasma proteins + protein bound substances

  5. kidney Definition of GFR Quantity of Glomerular Filtrate formed each Minute in all nephrons of both kidneys

  6. Calculation Of GFR • GFR= Filtration fraction x renal plasma flow • GFR= Permeability coefficient x NFP

  7. kidney GFR Contd…….. • = 20 % of Plasma flow • i.e. Filtration Fraction = 0.2 • i.e. GFR= Filtration Fraction × Renal Plasma Flow • = 125 ml/min • = 180 l/day

  8. kidney

  9. kidney Filtration Pressures PG= Glomerular Hydrostatic Pressure PB= Hydrostatic Pressure in Bowman’s Capsule • G= Colloid Osmotic Pressure in Glomerular Capillaries • B= Colloid Osmotic Pressure in Bowman’s Capsule

  10. kidney Pf = PG - PB - πG + πB = 60 – 18 - 32 + 0 = 10 mmHg

  11. kidney GFR= Kf ×P f • P f = Sum of Hydrostatic and Colloid Osmotic Forces • Kf = Permeability Co-Efficient = Permeability × Surface Area

  12. Determinants of GFRFactors affecting GFR

  13. kidney Factors affecting GFR Any factor that affects determinants of GFR will affect GFR i.e. factors affecting are • Filtration Co-Efficient ( Kf ) • Net Filtration Pressure ( Pf ) • Hydrostatic Pressure in Bowman’s Capsule • Colloid Osmotic Pressure in Glomerular Capillaries • Glomerular Hydrostatic Pressure • Colloid Osmotic Pressure in Bowman’s Capsule • Filtration Fraction • Renal Plasma Flow / Blood Flow • Dietary Factors

  14. kidney 1. Permeability Co-Efficient • Kf = Permeability Co-Efficient = Permeability × Surface Area =12.5 ml/min/mmHg of filtration pressure (400 times that of other body capillaries) ↑ Kf → ↑GFR (and vice versa) Diseases 1.Hypertension and diabetes mellitus → ↑thickness of glomerular capillary basement membrane →↓GFR 2. Renal diseases

  15. kidney 2. Net Filtration Pressure ( Pf ) Hydrostatic Pressure in Bowman’s Capsule • ↑PB → ↓ GFR (and vice versa) • Obstruction of urinary tract (kidney stones)

  16. kidney 2. Net Filtration Pressure ( Pf ) Colloid Osmotic Pressure in Glomerular Capillaries Increase  G → Decrease GFR (and vice versa) • 1. Arterial plasma colloidal osmotic pressure. • 2. Fraction of plasma filtered.

  17. kidney 2. Net Filtration Pressure ( Pf ) Glomerular Hydrostatic Pressure • ↑PG →↑GFR • Primary means for regulation of GFR • Factors affecting PG • Arterial pressure • Afferent arteriolar resistance • Efferent arteriolar resistance

  18. kidney 2. Net Filtration Pressure ( Pf ) Colloid Osmotic Pressure in Bowman’s Capsule • Normally little roll • May ↑in renal diseases

  19. kidney Effect of filtration fraction on GFR • Increase filtration factor concentrates the plasma proteins increases glomerular colloidal osmotic pressure decreases GFR

  20. kidney Renal Plasma flow or blood flow • Increase RPF/ Blood flow Increases GFR • Decrease RPF/ Blood flow Decreases GFR

  21. kidney Dietary Factors • High protein intake = RBF GFR • Blood glucose = RBF GFR

  22. kidney

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