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The 4 basic functions of the kidneys
• Ultrafiltration by glomerular capillaries
Dr. Ashok Solanki
Glomerular capillaries a network of high pressure
capillary bed fiters fluid ata rate about 180 lit/day
Dr. Ashok Solanki
Dr. Ashok Solanki
Dr. Ashok Solanki
Dr. Ashok Solanki
Glomerular filtration
• The glomerulus is a collection of twisted
capillaries
• that receive blood from the afferent arter...
Dr. Ashok Solanki
Glomerular fitration
Substances in the blood are
filtered through capillary fenestrae
between endothelial cells (single
la...
Junction- the JGA
Blood flows into the
glomerulus through
the afferent arterioles
and leaves the
glomerulus through the
ef...
Dr. Ashok Solanki
Dr. Ashok Solanki
Dr. Ashok Solanki
Dr. Ashok Solanki
14Dr. Ashok Solanki04.02.2013
04.02.2013 Dr. Ashok Solanki 15
Dr. Ashok Solanki
04.02.2013 Dr. Ashok Solanki 17
Renal handling of substances
18
Tubuloglomerular feedback
Dr. Ashok Solanki
GFR = Kf . (PG – PB – pG + pB)
The GFR is determined by
the sum of the hydrostatic pressure
colloid osmotic forces across ...
21
22
23
24
Autoregulation of GFR
• Afferent arteriolar feedback mechanism for regulating
GFR
• Efferent arteriolar feedback mechan...
25
26
27
Factors affecting GFR
1. Glomerular capillary hydrostetic pressure –
- arterial pressure
- afferent arterial resistance...
28
Factors affecting GFR
• Decrease Kf decrease GFR
• Increase Kf increase GFR
• In some diss. Lower Kf by reducing the
nu...
29
Autoregulation of GFR
Afferent arteriolar feedback mechanism for regulating
GFR
Efferent arteriolar feedback mechanism ...
Glomerular capillary filtration coefficient - Kf
The Kf is a measure of the product of the hydraulic conductivity and surf...
Dr. Ashok Solanki
Net filtration pressure
• Forces favoring filtration (mm Hg)
glomerular hydrostatic pressure - Pg 60
bowmen’s capsule coll...
Forces promoting & opposesing filtration
• Net filtration force is +ve causing filtration
Dr. Ashok Solanki
GFR is sum of Kf x Net filtration pressure
The amount of the glomerular filtrate by all the nephrons of both the kidneys
i...
Dr. Ashok Solanki
Dr. Ashok Solanki
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Glomerular Filtration is High and is Regulated Precisely

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Glomerular Filtration is High and is Regulated Precisely

  1. 1. The 4 basic functions of the kidneys • Ultrafiltration by glomerular capillaries Dr. Ashok Solanki
  2. 2. Glomerular capillaries a network of high pressure capillary bed fiters fluid ata rate about 180 lit/day Dr. Ashok Solanki
  3. 3. Dr. Ashok Solanki
  4. 4. Dr. Ashok Solanki
  5. 5. Dr. Ashok Solanki
  6. 6. Glomerular filtration • The glomerulus is a collection of twisted capillaries • that receive blood from the afferent arteriole of the renal blood supply • and exit the kidney via the efferent arteriole • Ultrafiltrate is the product of glomerular filtration of blood following its passage through a glomerular fi ltration barrier Dr. Ashok Solanki
  7. 7. Dr. Ashok Solanki
  8. 8. 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
  9. 9. 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
  10. 10. Dr. Ashok Solanki
  11. 11. Dr. Ashok Solanki
  12. 12. Dr. Ashok Solanki
  13. 13. Dr. Ashok Solanki
  14. 14. 14Dr. Ashok Solanki04.02.2013
  15. 15. 04.02.2013 Dr. Ashok Solanki 15
  16. 16. Dr. Ashok Solanki
  17. 17. 04.02.2013 Dr. Ashok Solanki 17
  18. 18. Renal handling of substances 18
  19. 19. Tubuloglomerular feedback Dr. Ashok Solanki
  20. 20. 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
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  24. 24. 24 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
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  27. 27. 27 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
  28. 28. 28 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
  29. 29. 29 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
  30. 30. 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
  31. 31. Dr. Ashok Solanki
  32. 32. 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
  33. 33. Forces promoting & opposesing filtration • Net filtration force is +ve causing filtration Dr. Ashok Solanki
  34. 34. 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
  35. 35. Dr. Ashok Solanki
  36. 36. Dr. Ashok Solanki

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