block2-pgy451-awayda

block2-pgy451-awayda - Block II Tubular Layout Tubular...

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Awayda, 2010- PGY451 Block II Tubular Layout Tubular Transport Proximal Tubule Loop of Henle Distal Tubule Collecting Duct Na + Excretion Renal Concentration and Dilution (Countercurrent)
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Awayda, 2010- PGY451 In a Nutshell Reabsorption and Secretion tied to GFR If the GFR is too high: Needed substances cannot be reabsorbed quickly enough and are lost in the urine If the GFR is too low: Everything is reabsorbed, including wastes that are normally disposed off
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Awayda, 2010- PGY451 Factors Affecting Reabsorption GFR Peritubular Pressure Transporter Numbers at the Membrane Transporter Activity Driving Forces Across Nephron Epithelial Cells
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Awayda, 2010- PGY451 Two Types of Nephrons From: http://www.biocourse.com/bcc/assets/
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Awayda, 2010- PGY451 Functional Differences Between Nephrons Cortical Nephrons ~ 85% of nephrons -located in the cortex Juxtamedullary nephrons ~ 15% of nephrons -located at the cortex-medulla junction -Have long loops of Henle that deeply invade the medulla -Have extensive thin segments -Are involved in the production of concentrated urine and conserving water (True proportions of nephron loops to convoluted tubules shown)
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Awayda, 2010- PGY451 Epithelial Transport Epithelial Cells underlie transport through all tubule segments All are a single cell layer in thickness All are “Polarized”
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Awayda, 2010- PGY451 What is “Polarized” Distinct luminal (apical) and serosal (basolateral) membranes. Separated by junctions.
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Awayda, 2010- PGY451 Routes of Epithelial Solute and Water Movement Transcellular Apical Basolateral Paracellular Tight and Leaky
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Awayda, 2010- PGY451 Tubular Transport Movement through 3 membranes + Diffusion I II III
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Awayda, 2010- PGY451 Direction of Tubular Transport Reabsorption, e.g., Na + , Cl - , K + , HCO3 - , and glucose Secretion, e.g., urea, uric acid, other organic ions, toxins Mechanisms Active transport Facilitated diffusion Passive-channel Passive-bilayer
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Awayda, 2010- PGY451 Properties of Transport Mechanisms Active transport Facilitated diffusion Passive-channel Passive-bilayer Properties Speed Selectivity Energy Use Regulation “Uphill” Saturation
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Awayda, 2010- PGY451 Saturation All transported molecules- except those that utilize passive diffusion across all three membranes- exhibit: A transport maximum (T m ): Is a reflection of the number (and activity) of available carriers in the renal tubules When T m of a substance is reached (saturation), the excess of that substance is excreted
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Awayda, 2010- PGY451 Transport Maximum Transport Maximum of Glucose Threshold Saturation Excretion
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Awayda, 2010- PGY451 Non-Reabsorbed Substances Substances are not reabsorbed if they: -Lack carriers -Are not lipid soluble
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This note was uploaded on 02/22/2011 for the course PGY 451 taught by Professor Baizer during the Spring '09 term at SUNY Buffalo.

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block2-pgy451-awayda - Block II Tubular Layout Tubular...

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