1. ﴿و ما أوتيتم من العلم إلا قليلا﴾
بسم الله الرحمن الرحيم
﴿و ما أوتيتم من العلم إلا قليلا﴾
صدق الله العظيم الاسراء اية 58

2. Lecturer of Medical Physiology
Kidney By
Dr. Abdel Aziz M. Hussein
Lecturer of Medical Physiology

5. Given these structures:
1. basement membrane
2. fenestra
3. filtration slit
Choose the arrangement that lists the structures in the order a molecule of glucose encounters them as the glucose passes through the filtration membrane to enter Bowman’s capsule.
a. 1,2,3
b. 2,1,3
c. 2,3,1
d. 3,1,2
e. 3,2,1

6. Urine Formation

7. Glomerular Filtration
Def.,
Means the bulk flow of a solvent through a filter carrying with it the solutes that are small enough to pass through the filter.

8. Glomerular Filtration Capillary endothelium
Blood
Capillary endothelium
Basement Membrane
Podocytes slits
Bowman Capsule

9. Glomerular Filtration
Def.,
It is an ultrafiltration since it is plasma minus plasma protein and cellular elements while simple filtration excludes only cellular elements.

10. Glomerular Filtration Capillary endothelium
Blood
Capillary endothelium
Basement Membrane
Podocytes slits
Blood Cells
Bowman Capsule
Plasma proteins
Plasma solutes

11. Glomerular Filtration
Dynamics:
Glomerular Filtration is formed by the forces of filtration as many capillary filtrate in the body (Starling's forces of filtration).
They are 4 forces;
2 Hydrostatic pressures
2 Oncotic pressures

12. Glomerular Filtration
Glomerular Oncotic Pressure (Gπ)
Glomerular Hydrostatic Pressure (Gp)
Glomerular capillary
Capillary endothelium
Basement Membrane
Podocytes slits
Bowman Capsule
Bowman oncotic Pressure (B π)
Bowman Hydrostatic Pressure (Bp)

13. Glomerular Filtration
Gπ = 32 mmHg
Gp = 60 mmHg
Gp = 18 mmHg
Bπ = 0 mmHg

14. Glomerular Filtration
GFR is determined by Starling's principle;
″The rate & direction of fluid movement is proportional to the algebraic sum of hydrostatic & oncotic pressures″
So, GFR α (hydrostatic pressure – oncotic pressure)
GFR α { (Gp- Bp) – (Gπ – Bπ)}
KF = filtration coefficient

15. Glomerular Filtration
Net filtering force {60-(32+18)} = 10 mmHg and GFR = 120 mL/ min

16. Glomerular and Systemic Filtration
Glomerular filtration
Systemic capillary filtration
Capillary Exchange Area
1.6 m2 – of which only 2-3% are available for filtration ( cm2)
1000 m2 of systemic capillary 25%- 35% are opened  m2
Pulmonary capillary Surface area is 60 m2.
Filtration Rate
180 L/day
20 L/day are filtered at arterial end, of which 18L are reabsorbed at venous end & 2L by lymphatic.
Capillary Hydrostatic Pressure
45-60 mmHg
32 mmHg at art. end & decrease to 15 mmHg at venous end
Osmotic Pressure of Plasma Protein
25 mmHg at afferent end of capillary & rises to 37 mmHg at efferent end of capillary.
25 mmHg along the whole length
Filtration Coefficient
4mL/min/1 mmHg/100 gm
0.01mL/min/1mmHg/100 gm.

17. Glomerular Filtration
Gp = 60 mmHg
Gπ = 37 mmHg
Gπ = 25 mmHg

18. Systemic Filtration

19. Glomerular Filtration Rate
(GFR)

20. Glomerular Filtration Rate
Def.,
Volume of plasma filtered by both kidney per unit time
Value:
125 ml/min
180 L/day or
60 nl/min for single nephron (SNGFR).
Filtration fraction: is part of RPF filtered in Glomeruli
GFR ml/min
= = = 1/5 or 20%
RPF ml/min

21. RPF
650 ml/min
FF= 120/ 650 = 20%
GFR
120 ml/min
RPF
649 ml/min
Urine flow rate
1 ml/min

22. Glomerular Filtration Rate
Significance of High GFR:
To ensure processing of plasma (3L) about 60 times/day (since daily GFR = 180L/day  prevents accumulation of metabolites.
Causes of high GFR:
High filtration coefficient:
KF is volume of fluid filtered /min/ mmHg pressure difference across the membrane

23. Glomerular Filtration Rate
Causes of high GFR:
High filtration coefficient:
For the kidney  4 ml/ min/ mmHg/ 100 gm tissue or 12 ml/ min/ mmHg/ 300gm (both kidneys).
For systemic capillary  0.01 ml/ min/ mmHg/ 100gm tissue.
This is due to high permeability of the glomerular membrane for same hydrostatic pressure gradient.

24. Glomerular Filtration Rate
Causes of high GFR:
2) High capillary hydrostatic P.:
It is about mmHg in glomerular capillary
In systemic capillary 32 mmHg at arterial end and 15 mmHg at venous end
Causes of high GP:
Renal artery → short, wide, direct branch from aorta.
Afferent arteriole → straight branch of interlobular artery
Efferent arteriole → narrower than afferent arteriole
Glomerular capillaries →present between two arteries

25. Causes of High Gp

26. Causes of High Gp

27. Glomerular Filtration Rate
Causes of high GFR:
3) High RPF.:
It is about 600ml/ min.
This high RBF eventually leads to high GFR.
RBF

28. Glomerular Filtration Rate
Factors Affecting GFR:
Glomerular hydrostatic pressure
About 45 – 60 mmHg
Help GFR
Bowman’s capsular hydrostatic pressure
About 18 mmHg
Oppose GFR
Oncotic pressure of plasma protein
About 32 mmHg
Renal plasma flow (RPF)
About 650 ml/min
Filtration coefficient
About 4 ml/min/ 1mmHg/ 100 gm

29. 1. Glomerular Hydrostatic P.
It is high compared to systemic capillary
Causes of high GP
Factors affecting:
A) Systemic ABP:
Between mmHg ( no change)
Less than 80 mmHg → ↓ Gp
More than 180 mmHg →↑ Gp
B) Balance between afferent and efferent arterioles resistance

31. 2. Bowman Hydrostatic P.
It is about 18 mmHg  helps to maintain renal tubules patent.
Acts as a driving force to propel glomerular filtrate along whole length of renal tubules.
If increased e.g. in ureteric obstruction  decrease GFR.

32. Bp
Increased Bp

33. 3. Oncotic P. of Plasma Proteins
Normally 32 mmHg.
If changed  marked effect on GFR.
Increase plasma oncotic pressure  decrease GFR.
As in:
Marked hyperproteinemia as in multiple myeloma.
Dehydration, hemorrhage, sever burns & chronic diarrhea.

34. Gπ

35. 3. Oncotic P. of Plasma Proteins
Leakage of plasma albumin from glomerular membrane in some pathological conditions  decrease plasma oncotic pressure & increase Bowman’s oncotic pressure  increase GFR.

36. 4. Renal Plasma Flow RPF affect indirectly the plasma oncotic pressure
Increase RPF  maintain normal plasma oncotic pressure and filtration equilibrium is achieved too late  helps GFR.
Decrease RPF  elevates plasma oncotic pressure  decrease GFR.

37. High RPF

38. 5. Filtration Coefficient
It is the effectiveness of the permeability of the barrier.
It depends on:
Hydraulic conductivity (water permeability of the barrier).
Effective filtration surface area

39. 5. Filtration Coefficient
2. Effective filtration surface area is affected by:
Total number of functioning glomeruli.
State of intraglomerular mesangium.
Their contraction (e.g. by AII)  decrease effective filtration area & their relaxation (e.g. by dopamine)  increase effective surface area.

40. Effect of Afferent and Efferent Arteriolar Resistance on: RPF, GFR, and Filtration Fraction (FF)

41. Change in Preglomerular Resistance Or (afferent arteriole diameter)
V.D. of afferent arterioles
↑ Gp
↑ RPF
FF = no change
↑ GFR

42. Change in Preglomerular Resistance Or (afferent arteriole diameter)
V.C. of afferent arterioles
↓ Gp
↓ RPF
FF = no change
↓ GFR

43. Change in Postglomerular Resistance Or (efferent arteriole diameter)
V.D. of efferent arterioles
↓ Gp
↑ RPF
FF = decrease
↓ GFR

44. Change in Postglomerular Resistance Or (efferent arteriole diameter)
V.C. of efferent arterioles
↑ Gp
↓ RPF
FF = Increase
↑ GFR

46. RPF GFR FF (GFR / RBF) VC --  constant VD 
Afferent (Preglomerular resistance)
Efferent (Postglomerular resistance
RPF
GFR FF
(GFR / RBF) VC -- 
constant VD 

47. إيمحتب

48. THANKS