1. kidney

2. kidney

3. Peshawar Medical College NWFP Pakistan
URINE FORMATION
Peshawar Medical College NWFP Pakistan

5. kidney.lecture 5b
19 February 2019
dr.rashid mahmood

7. Glomerular Filtrate
Plasma minus plasma proteins + protein bound substances

8. kidney.lecture 5b
19 February 2019
Definition of GFR
Quantity of Glomerular Filtrate formed each Minute in all nephrons of both kidneys
kidney
dr.rashid mahmood

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

10. GFR Contd…….. = 20 % of Plasma flow i.e. Filtration Fraction = 0.2
kidney.lecture 5b
19 February 2019
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
kidney
dr.rashid mahmood

11. kidney.lecture 5b
19 February 2019
kidney
dr.rashid mahmood

12. Filtration Pressures PG= Glomerular Hydrostatic Pressure
kidney.lecture 5b
19 February 2019
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
kidney
dr.rashid mahmood

13. Pf = PG - PB - π G + π B = 60 – 18 - 32 + 0 = 10 mmHg
kidney.lecture 5b
19 February 2019
Pf = PG - PB - π G + π B = 60 – = 10 mmHg
kidney
dr.rashid mahmood

14. P f = Sum of Hydrostatic and Colloid Osmotic Forces
kidney.lecture 5b
19 February 2019
GFR= Kf × P f
P f = Sum of Hydrostatic and Colloid Osmotic Forces
Kf = Permeability Co-Efficient
= Permeability × Surface Area
kidney
dr.rashid mahmood

15. Determinants of GFR Factors affecting GFR
kidney.lecture 5b
19 February 2019
Determinants of GFR Factors affecting GFR
dr.rashid mahmood

16. 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
kidney

17. 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
kidney

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

19. 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.
kidney

20. 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
kidney

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

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

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

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

25. kidney