205textnotes39 - Filtration fraction : (Figure 19-5)...

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Excretion of a substance depends on the amount that was filtered, reabsorbed and secreted (Figure 19-3) ------------------------------------------------------------------------------ B. Filtration, Reabsorption, Secretion, Excretion ------------------------------------------------------------------------------- Bowman's capsule (Figure 19-4) - glomerular filtration - occurs in the glomerulus - glomerulus = very porous capillary bed - involves bulk flow of protein-free plasma out of capillary and into Bowman's space - efferent arteriole is narrower in diameter than the afferent arteriole generating a pressure gradient across the glomerulus. " glomerular filtrate " = same composition as plasma and very few plasma proteins - approx. 20% of plasma in the glomerulus capillaries is filtered (180 L/day).
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Unformatted text preview: Filtration fraction : (Figure 19-5) " net glomerular filtration pressure " Filtration pressure (Figure 19-6)- net bulk flow of protein-free plasma out of capillaries - hydrostatic pressure in the glomerulus is 55 mmHg (error in textbook) - hydrostatic pressure in Bowman's space is 15 mmHg - net hydrostatic pressure = 55 - 15 = 40 mmHg - But, there is a high protein content in the capillary as compared to Bowman's space. - therefore, net osmotic flow into glomerular capillaries = 30 mmHg Net Filtration Pressure = 40 - 30 = 10 mmHg Glomerular Filtration Rate = volume of plasma filtered into the Bowman's space per unit time (mL/min) = 125 mL/min = 180 L/day - kidney receives 20 - 25 % of cardiac output - filters the entire plasma volume 60x per day...
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