Physi
Organization of the Urinary System, Clearance, GFR, and Renal Blood Flow
Jamie Mitchell, MSc, PhD Physiol 210
Distribution of CO
Renin
Basement Membrane
3 Basic Renal Functions:
Assessing Renal Function: Renal Clearance
• Clearance measurements - compare the rate at which the glomeruli filter a substance (water or a solute) with the rate at which the kidneys excrete it into the urine • The “virtual” volume of plasma from which a substance is completely removed by the kidney in a given amount of time (usually a minute). • Measurements indicate/evaluate renal function • Used clinically to estimate renal plasma flow (RPF) and glomerular filtration rate (GFR)
Px = plasma concentration of X; RPF = renal plasma flow Ux = urine concentration of X; V = urine flow
Clinical Uses of Clearance: The Clearance Equation
(p-aminohippurate (PAH))
Glomerular Filtration Rate (GFR)
Note: Ideal glomerular marker would fit into the clearance equation
The Clearance of Inulin is a Measure of Glomerular Filtration Rate
Criteria for Ideal Marker: 1. Substance must be freely filterable in the glomeruli. 2. Substance must be neither reabsorbed nor secreted by the renal tubules. 3. Substance must not be synthesized, broken down, or accumulated by the kidney. 4. Substance must be physiologically inert (not toxic and without effect on renal function).
Clearance of Creatinine is a Useful Clinical Index of GFR
CCr = GFR= UCr x V -----PCr
– If Cx > GFR, then substance was secreted
– If Cx < GFR, then substance was reabsorbed
GFR and Renal Blood Flow
Glomerular Filtration Rate (GFR) 125ml/min [180 L/24 hours]
Urine= 1.5 L/24 hours
Filtration Fraction of Plasma = 125/625 = 20%
Renal Plasma Flow (RPF) 625 ml/min
Molecular Size, Electrical Charge, and Shape Determine the Filterability of Solutes Across the Glomerular Filtration Barrier
- Charge - Charge
UF = Ultrafiltrate
Filterability
- Charge -
Jamie Mitchell, MSc, PhD Physiol 210
Distribution of CO
Renin
Basement Membrane
3 Basic Renal Functions:
Assessing Renal Function: Renal Clearance
• Clearance measurements - compare the rate at which the glomeruli filter a substance (water or a solute) with the rate at which the kidneys excrete it into the urine • The “virtual” volume of plasma from which a substance is completely removed by the kidney in a given amount of time (usually a minute). • Measurements indicate/evaluate renal function • Used clinically to estimate renal plasma flow (RPF) and glomerular filtration rate (GFR)
Px = plasma concentration of X; RPF = renal plasma flow Ux = urine concentration of X; V = urine flow
Clinical Uses of Clearance: The Clearance Equation
(p-aminohippurate (PAH))
Glomerular Filtration Rate (GFR)
Note: Ideal glomerular marker would fit into the clearance equation
The Clearance of Inulin is a Measure of Glomerular Filtration Rate
Criteria for Ideal Marker: 1. Substance must be freely filterable in the glomeruli. 2. Substance must be neither reabsorbed nor secreted by the renal tubules. 3. Substance must not be synthesized, broken down, or accumulated by the kidney. 4. Substance must be physiologically inert (not toxic and without effect on renal function).
Clearance of Creatinine is a Useful Clinical Index of GFR
CCr = GFR= UCr x V -----PCr
– If Cx > GFR, then substance was secreted
– If Cx < GFR, then substance was reabsorbed
GFR and Renal Blood Flow
Glomerular Filtration Rate (GFR) 125ml/min [180 L/24 hours]
Urine= 1.5 L/24 hours
Filtration Fraction of Plasma = 125/625 = 20%
Renal Plasma Flow (RPF) 625 ml/min
Molecular Size, Electrical Charge, and Shape Determine the Filterability of Solutes Across the Glomerular Filtration Barrier
- Charge - Charge
UF = Ultrafiltrate
Filterability
- Charge -