Is more selective Allows diffusion of only Small plasma proteins Nutrients Ions

Is more selective allows diffusion of only small

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Is more selective Allows diffusion of only Small plasma proteins Nutrients Ions The Filtration Slits Are the finest filters Have gaps only 6–9 nm wide Prevent passage of most small plasma proteins Filtration Pressure Glomerular filtration is governed by the balance between Hydrostatic pressure (fluid pressure) Colloid osmotic pressure (of materials in solution) on either side of capillary walls Glomerular Hydrostatic Pressure (GHP) Is blood pressure in glomerular capillaries Tends to push water and solute molecules
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Out of plasma Into the filtrate Is significantly higher than capillary pressures in systemic circuit Due to arrangement of vessels at glomerulus Glomerular Blood Vessels Blood leaving glomerular capillaries Flows into an efferent arteriole with a diameter smaller than afferent arteriole Efferent arteriole produces resistance Requires relatively high pressures to force blood into it Capsular Hydrostatic Pressure (CsHP) Opposes glomerular hydrostatic pressure Pushes water and solutes Out of filtrate Into plasma Results from resistance to flow along nephron and conducting system Averages about 15 mm Hg Net Hydrostatic Pressure (NHP) Is the difference between Glomerular hydrostatic pressure and capsular hydrostatic pressure Colloid Osmotic Pressure of a Solution Is the osmotic pressure resulting from the presence of suspended proteins Blood colloid osmotic pressure (BCOP) Tends to draw water out of filtrate and into plasma Opposes filtration Averages 25 mm Hg Filtration Pressure (FP) Is the average pressure forcing water and dissolved materials Out of glomerular capillaries Into capsular spaces At the glomerulus is the difference between Hydrostatic pressure and blood colloid osmotic pressure across glomerular capillaries Glomerular Filtration Rate (GFR) Is the amount of filtrate kidneys produce each minute Averages 125 mL/min About 10% of fluid delivered to kidneys Leaves bloodstream Enters capsular spaces Creatinine Clearance Test
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Is used to estimate GFR A more accurate GFR test uses inulin Which is not metabolized Filtrate Glomeruli generate about 180 liters of filtrate per day 99% is reabsorbed in renal tubules Filtration Pressure Glomerular filtration rate depends on filtration pressure Any factor that alters filtration pressure alters GFR Control of the GFR Autoregulation (local level) Hormonal regulation (initiated by kidneys) Autonomic regulation (by sympathetic division of ANS) Autoregulation of the GFR Maintains GFR despite changes in local blood pressure and blood flow By changing diameters of afferent arterioles, efferent arterioles, and glomerular capillaries Reduced blood flow or glomerular blood pressure triggers Dilation of afferent arteriole
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