Outline Chapter 3 - Topic 3 Glomerular Filtration and Renal...

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Unformatted text preview: Topic 3 Glomerular Filtration and Renal Blood Flow • What is urine?- • What is the importance of GFR?-- ¡ A fall in GFR indicates… ¡ An increase in GFRindicates … Renal Clearance • Definition: • The Fick Principle • The _________________ is the single input source to the kidney. • The ____________________________ are two output routes. • Principle of Mass Balance • The equation for renal clearance: C = [U] x x V [P] x C = clearance (ml/min) [U] = urine concentrations (mg/ml) V = urine flow rate per minute (mg/ml) [P] = plasma concentration (mg/ml) x = substance to be cleared • The formula indicates that the renal clearance is the ratio of urinary excretion ([U] x V) to plasma concentration [P ]. • For a substance; if the renal clearance increases, what will happen to the urinary excretion? - • The units of clearance are _____________________________, which means what? - The Importance of the Concept of Clearance: ¡ ¡ Excretion Rate • If a substance is present in the urine at a concentration of 100 mg/ml and the urine flow rate is 1 ml/min, we can calculate t he excretion rate: Excretion rate = U x x V = = • If a substance is present in the plasma at a concentration of 1 mg/ml, calculate its clearance: C x = [U] x x V = = [P] x • Means how much of plasma is completely cleared of substance x each minute? ________________ Glomerular Filtration Rate Clearance of Inulin • Why use it? • Chemical composition: • Produced by the body? • Filtration: • Is it reabsorbed, secreted, or metabolized by nephron cells? Amount filtered = Amount excreted GFR x [P in ] = [U in ] x V where, GFR = [U in ] x V [P in ] P in and U in = plasma and urine concentrations of inulin V = urine flow • Can the clearance of inulin provide a means of determining the GFR? • Glomerular marker for the measurement of GFR: Criteria 1. 2. 3. 4. Filtration Fraction Under normal conditions, what percent of the plasma that enters the glomerulus is filtered? What is this called? FF = GFR = 0.15 to 0.20 RPF • What percent of the plasma does not pass through a glomerulus? Creatinine • A byproduct of_____________________________. • Used to estimate ____________________________. • Production:- • Secretion: - Error introduced is about 10% - Method used to quantitate plasma creatinine overestimates the true value by 10% - the two errors cancel • Creatinine clearance provides a reasonably accurate measure of the GFR. Clearance of Other Substances Albumin • Clearance: - Is it filtered across the glomerular capillaries? Glucose • Clearance:______________________ Reason?- Filtration: Reabsorption: Na + , Urea, P ι , Cl- • Clearance:- PAH (Para-AminoHippuric acid) • Clearance:- Filtration: Secretion: Glomerular Filtration • What is the first step in the formation of urine?...
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Outline Chapter 3 - Topic 3 Glomerular Filtration and Renal...

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