The document discusses renal handling of substances and factors that affect glomerular filtration rate (GFR). It describes how substances are filtered through the glomerular capillaries and pass through the basement membrane into Bowman's capsule. GFR is determined by the glomerular filtration coefficient and net filtration pressure, which is influenced by hydrostatic and oncotic pressures across the glomerular membrane. Autoregulation mechanisms and tubuloglomerular feedback help regulate GFR in response to changes in arterial pressure or fluid delivery to the macula densa.

1. Renal handling of substances
Dr. Ashok Solanki

2. Dr. Ashok Solanki

3. Dr. Ashok Solanki

4. Dr. Ashok Solanki

5. Dr. Ashok Solanki

6. Dr. Ashok Solanki

7. Factors affecting G.F.R.
 Changes in renal blood flow
 Changes in glomerular capillary hydrostatic pressure
 Changes in systemic blood pressure
 Afferent or efferent arteriolar constriction
 Changes in hydrostatic pressure in Bowman's capsule
 Ureteral obstruction
 Edema of kidney inside tight renal capsule
Changes in concentration of plasma proteins: dehydration,
hypoproteinemia, etc (minor factors)
 Changes in Kf
 Changes in glomerular capillary permeability
 Changes in effective filtration surface area
Dr. Ashok Solanki

8. Dr. Ashok Solanki

9. Glomerular fitration
Substances in the blood are
filtered through capillary fenestrae
between endothelial cells (single
layer).
filtrate then passes across the
basement membrane and
through slit pores between the
foot processes
(also called pedicels) and enters
the capsular space.
From here, the filtrate is
transported to the lumen of the
proximal convoluted tubule.
Dr. Ashok Solanki

10. Dr. Ashok Solanki

11. Autoregulation of GFR
• Afferent arteriolar feedback mechanism for regulating
GFR
• Efferent arteriolar feedback mechanism for regulating
GFR
• Myogenic mechanism regulating GFR- resist stretching
during increase arterial pressure – stretch of vascular
wall increase calcium ions entry from ECF into the cell –
contract the cells – increase vascular resistance –
decrease GFR and RBF
Dr. Ashok Solanki

12. Dr. Ashok Solanki

13. GFR = Kf . (PG – PB – pG + pB)
The GFR is determined by
the sum of the hydrostatic pressure
colloid osmotic forces across the glomerular membrane
Bowmens capsule hydrostatic pressure
the glomerular capillary filtration coefficient, Kf
GFR = Kf . Net filtration pressure
Dr. Ashok Solanki

14. The 4 basic functions of the kidneys
• Ultrafiltration by glomerular capillaries
Dr. Ashok Solanki

15. glomerular filtration and tubular
function.
• bulk flow of fluid from glomerular capillary to Bowman’s
space
• volume = 20% of RPF (filtration fraction), ≈ 125 ml/min
• barriers to filtration
• endothelial fenestrae
• basement membrane
• Podocytes
• GFR = Kf · NFP (filtration coefficient x net filtration pressure)
Dr. Ashok Solanki

16. Dr. Ashok Solanki

17. Dr. Ashok Solanki

18. Dr. Ashok Solanki

19. Dr. Ashok Solanki

20. Dr. Ashok Solanki

21. Dr. Ashok Solanki

22. Junction- the JGA
Blood flows into the
glomerulus through
the afferent arterioles
and leaves the
glomerulus through the
efferent
arterioles.
The proximal tubule
exits Bowman’s
capsule.
Dr. Ashok Solanki

23. Tubuloglomerular feedback
o Alterations in GFR due to changes in glomerular perfusion
pressure will lead to an alteration in the composition of the fluid
delivered to the macula densa region of the nephron tubule
o The macula densa senses these changes and acts to alter
afferent arteriole tone to vary glomerular perfusion pressure to
return the GFR to normal
o
Dr. Ashok Solanki

24. Dr. Ashok Solanki

25. The structure of the filter
1. The glomerular capillary endothelium:
• A highly specialised capillary endothelium with fenestrations (windows)
to minimise the filter thickness;
• This layer prevents cellular components of blood coming into contact with
the basement membrane.
2. The glomerular basement membrane:
• Made of connective tissue, it is negatively charged;
• This is the layer that actually acts as the filter.
3. Bowman’s epithelial cells (podocytes):
• Epithelial cells with multiple projections (foot processes) which interlink
with each other
• whilst still keeping a small gap between them creating a large surface
area;
• Act to maintain the basement membrane, and has phagocytic functions .
Dr. Ashok Solanki

26. Dr. Ashok Solanki

27. Dr. Ashok Solanki

28. Dr. Ashok Solanki

29. Dr. Ashok Solanki

30. Dr. Ashok Solanki

31. Dr. Ashok Solanki

32. Tubuloglomerular feedback
Dr. Ashok Solanki

33. Dr. Ashok Solanki

34. Dr. Ashok Solanki

35. Dr. Ashok Solanki

36. Dr. Ashok Solanki

37. Factors affecting GFR
1. Glomerular capillary hydrostetic pressure –
- arterial pressure
- afferent arterial resistance
- efferent arterial resistance
2. Colloidal osmotic pressure of glomerulus –
3. bowmen’s capsular hydrostetic pressure – ureteric stone,
obstruction of urinary tract
4. RBF – GFR directly related to RBF
5. Sympathetic stimulation
Dr. Ashok Solanki

38. Factors affecting GFR
• Decrease Kf decrease GFR
• Increase Kf increase GFR
• In some diss. Lower Kf by reducing the
number of functional glo. Capillaries
• Increase thickness of the glo. Capillaries
• Chronic uncontrolled hypertension and
diabetes mellitus
Dr. Ashok Solanki

39. Autoregulation of GFR
Afferent arteriolar feedback mechanism for regulating
GFR
Efferent arteriolar feedback mechanism for regulating
GFR
Myogenic mechanism regulating GFR- resist stretching
during increase arterial pressure – stretch of vascular
wall increase calcium ions entry from ECF into the cell –
contract the cells – increase vascular resistance –
decrease GFR and RBF
Dr. Ashok Solanki

40. Glomerular capillary filtration coefficient - Kf
The Kf is a measure of the product of the hydraulic conductivity and surface
area of the glomerular capillaries
Kf = GFR / Net filtration pressure
GFR – 125 ml / min
Net filtration pressure – 10 mm of Hg
Kf – 12.5 ml / min /mm of Hg
4.2 ml/min/mm of Hg/100g of kidney wt.
Dr. Ashok Solanki

41. Dr. Ashok Solanki

42. Net filtration pressure
• Forces favoring filtration (mm Hg)
glomerular hydrostatic pressure - Pg 60
bowmen’s capsule colloid
osmotic pressure – πb 0
• Forces opposing filtration (mm Hg )
bowmen’s capsule hdrostatic
pressure - Pg 18
glomerular capillary colloid
osmotic pressure – πg 32
Net filtration pressure = 60 – 18 – 32 = +10 mmof Hg
Dr. Ashok Solanki

43. Forces promoting & opposesing filtration
• Net filtration force is +ve causing filtration
Dr. Ashok Solanki

44. GFR is sum of Kf x Net filtration pressure
The amount of the glomerular filtrate by all the nephrons of both the kidneys
in a one minute is called GFR
GFR = filtration fraction x RBF
In the average human adult, the GFR is about 125 ml / min. or 180 L / day
Filtration fraction – the fraction of the renal plasma which becomes the filtrate
Filtration fraction = GFR / RBF
Dr. Ashok Solanki

45. Dr. Ashok Solanki

46. Dr. Ashok Solanki

47. Dr. Ashok Solanki