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Determinants of GFR. GFR = Capillary filtration coefficient X Net filtration pressure. Increased glomerular Capillary filtration coefficient increases GFR. Probably not a primary mechanism for day-to-day regulation of GFR.

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determinants of gfr
Determinants of GFR
  • GFR = Capillary filtration coefficient X Net filtration pressure.
  • Increased glomerular Capillary filtration coefficient increases GFR.
    • Probably not a primary mechanism for day-to-day regulation of GFR.
    • Glomerular Capillary filtration coefficient is changed in some disease states such as diabetes millitus.
determinants of gfr1
Determinants of GFR
  • GFR = Capillary filtration coefficient X Net filtration pressure.
  • Increased hydrostatic pressure in Bowman’s capsule decreases GFR (inverse is also true).
    • Normally, not a primary mechanism for day-to-day regulation of GFR.
    • Hydrostatic pressure in Bowman’s capsule can change in some pathologic conditions such as obstruction of the urinary tract.

Guyton’s Textbook of Medical Physiology 26-12

determinants of gfr2
Determinants of GFR
  • GFR = Capillary filtration coefficient X Net filtration pressure.
  • Increased glomerular capillary colloid osmotic pressure decreases GFR.
    • Two factors regulate glomerular capillary colloid osmotic pressure:
      • Arterial plasma colloid osmotic pressure.
      • Filtration fraction.

Guyton’s Textbook of Medical Physiology 26-12 & 13

determinants of gfr3
Determinants of GFR
  • Increased glomerular capillary colloid osmotic pressure decreases GFR (cont.)
    • Filtration fraction = GFR/renal blood flow
    • Such that, a lower rate of blood flow into the glomerulus causes an increase in the filtration fraction
      • decreased plasma volume with constant filtration volume increasing the protein concentration.
      • results in an increase in Glomerular colloid osmotic pressure which tends to decrease GFR.
        • inverse is also true.
determinants of gfr4
Determinants of GFR
  • GFR = Capillary filtration coefficient X Net filtration pressure.
  • Increased glomerular capillary hydrostatic pressure increases GFR.
    • Three variables determine the glomerular hydrostatic pressure.
  • Arterial pressure.
  • Afferent arterial resistance.
  • Efferent arterial resistance.

Guyton’s Textbook of Medical Physiology 26-12

determinants of gfr5
Determinants of GFR
  • Increased arterial pressureincreases glomerular capillary hydrostatic pressure resulting in increased GFR.

Sherwood’s Human Physiology 14-10 & 14-11 5th Ed & 14-9 & 14-10 6th Ed

determinants of gfr6
Determinants of GFR
  • Increased afferent arterial resistancedecreases blood flow to the glomerular capillary resulting in decreased glomerular capillary hydrostatic pressure and reduced GFR.

Sherwood’s Human Physiology 14-10 & 14-11 5th Ed & 14-9 & 14-10 6th Ed

determinants of gfr7
Determinants of GFR
  • Decreased afferent arterial resistance(dilation) _increases_ glomerular capillary hydrostatic pressure and GFR.

Sherwood’s Human Physiology 14-10 & 14-11 5th Ed & 14-9 & 14-10 6th Ed

determinants of gfr8
Determinants of GFR
  • Moderate increases in efferent arterial resistance(constriction) increase glomerular capillary hydrostatic pressure and slightly increases GFR.

Guyton’s Textbook of Medical Physiology 26-12

determinants of gfr9
Determinants of GFR
  • A severe increase in efferent arterial resistance (constriction)increases glomerular capillary hydrostatic pressure, but also increases the colloid osmotic pressure (due to the decreased renal blood flow). This results in a net decrease in GFR.

Guyton’s Textbook of Medical Physiology 26-14

renal blood flow
Renal blood flow
  • The Kidneys get ~22% of the cardiac output.
    • Greater than what is needed to supply kidneys with nutrients and remove waste products.
    • Great volume is necessary to supply enough plasma for high GFRs.
    • The renal cortex receives most of the blood.
    • The renal medulla receives only 1-2% of the blood.
  • Renal blood flow is determined by the pressure gradient across the renal vasculature divided by the total renal vascular resistance.
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