Renal Structure and Function Sodium Transport
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Renal Structure and Function Sodium Transport UTSouthwestern STARS Program Orson W. Moe, M.D. Department of Internal Medicine Division of Nephrology organism world Composition Quantity Maintain constancy Disease Physiologic Afferent parameter Efferent Sensor Effector Renal Function Good stuff Bad stuff Endocrine hormone Metabolic substrate Excretion Endocrine Metabolism Gross anatomy Medulla (Pyramids) Medulla Outer Papilla Outer stripe Inner stripe Capsule Inner Medullary rays Cortex Major calyx Renal pelvis Column of Bertin Minor calyx Ureter Renal Vasculature Afferent arteriole Cortical ascending Arcuate Renal artery Segmental branches Main branch Interlobar Interlobar Arcuate Cortical ascending Afferent arteriole Arcuate Efferent arteriole Renal Circulation Little or no anastomoses Highest blood flow per gram tissue Multiple capillaries in tandem Functional arteriovenous shunts Renal Circulation Little or no anastomoses Highest flow per gram tissue Multiple capillaries in tandem Functional AV shunts Renal Circulation Little or no anastomoses Highest flow per gram tissue Multiple capillaries in tandem Functional AV shunts 25-30% Cardiac output <2% Body mass Renal venous pO2 Highest (60-70 mm Hg) Renal A-VO2 difference Lowest (10-15%) Glomerular Renal Circulation capillary Little or no anastomoses Highest flow per gram tissue Peritubular Multiple capillaries in tandem capillary Functional AV shunts Renal Circulation Little or no anastomoses Highest flow per gram tissue Multiple capillaries in tandem Functional AV shunts Glomerular Peritubular capillary capillary Afferent Cortical Efferent arteriole ascending arteriole Vasa recta Functional AV shunts Excretion Ultrafiltration Secretion Reabsorption Nephron Secretory Filtration-Reabsorption Nephron Secretory Dump Filtration-Reabsorption Nephron Secretory Dump Filtration-Reabsorption 300 marbles Remove 294 300 marbles Remove 294 300 marbles Remove 294 Put 6 back What does that mean? 5% error 1 L/day 1 L/day Error = 50 ml 0.95 L/day 0.95 L/day 5% error 170 L/day 1 L/day Error = 9L 10 L/day 169 L/day 160 L/day Amount excreted Fractional excretion Amount filtered Filtration-Secretion Amount Amount filtered > 1 excreted Filtration Amount Amount = 1 filtered excreted Filtration-Reabsorption Amount Amount filtered excreted < 1 Walk the nephron Overview Afferent arteriole Distal convoluted tubule Cortical nephron Glomerulus Cortical collecting tubule Juxtamedullary nephron Proximal convoluted Proximal Efferent tubule convoluted arteriole tubule Proximal straight tubule Cortex Proximal straight tubule Outer Thick ascending limb Medulla Descending thin limb Medullary collecting tubule Thin Loop of Henle Inner ascending Medulla limb The Glomerulus Form an ultrafiltrate Afferent arteriole Parietal epithelium Visceral epithelium Tubule Bowman’s space Urinary lumen Efferent arteriole GBM Mesangium Visceral Tubule lumen epithelial cells Bowman's space (podocytes) Bowman's capsule Parietal epithelial cells Visceral epithelial cell (foot processes) Afferent Nerve arteriole Capillary fibers basement Juxtaglomerular granular membrane cells Capillary Macula endothelial densa cells cells Glomerular capillary Distal end lumen of the thick Smooth ascending limb Mesangial muscle cells extracellular Mesangial Efferent arteriole matrix cells Extraglomerular mesangium Bowman space Podocyte Capillary Foot process Podocyte Endothelial cell Mesangial matrix Mesangial cell Podocyte Foot process Endothelium Blood cells Large proteins Small proteins Basement membrane Electrolytes Water Endothelium Podocyte foot process Transition to tubule Renal Tubules Modify the ultrafiltrate into final urine Overview Afferent arteriole Distal convoluted tubule Cortical nephron Glomerulus Cortical collecting tubule Juxtamedullary nephron Proximal convoluted Proximal Efferent tubule convoluted arteriole tubule Proximal straight tubule Cortex Proximal straight tubule Outer Thick ascending limb Medulla Descending thin limb Medullary collecting tubule Thin Loop of Henle Inner ascending Medulla limb Proximal Distal convoluted tubule tubule Intercalated Principal cell Proximal cell Cortical straight collecting tubule tubule Thick Inner ascending medullary limb collecting tubule Descending Ascending thin limb thin limb Brush border Protrusions Features of tubular epithelia Tight junctions Intercellular space Infoldings Interdigitation Polarized Apical Basolateral Amplification of surface area Brush border Infolding Interdigitation Transport Transcellular Paracellular Currency for Solute Transport High energy metabolic substrates ATP Electrochemical gradients Glutamine ATP 3Na+ 2K+ Low [Na+] Urine -ve voltage Interstitium/ Plasma ATPase Cotransporter Countertransporter Channel Na+ H+ + + + Na+ K ATP Na Glucose Na Paracellular Transport Proteins Coupled Transporters Ca2+ H+ OH- Na+ Cl- NaCl Yanomami Indians Daily ingestion & excretion Yanomani Dallasite K+ 400-500 mEq/day 40 mEq/day Na+ <10 mEq/day 200 mEq/day NaCl 100% 50-60% 7-10% 2-5% Cortex 30% Medulla 1-2% Proximal Distal nephron nephron Transcellular Interstitium/Capillary pathway Paracellular pathway Urinary Lumen Low gradient High gradient High capacity Low capacity Capillary 3Na+ 3Na+ 3Na+ 3Na+ Cl- Cl- ~ ~ ~ ~ 2K+ 2K+ 2K+ 2K+ + K + Na+ Na+ X Na+ 2Cl- Na+ Cl- Na X Lumen Proximal Distal Low gradient High gradient High capacity Low capacity Proximal tubule Thick ascending limb Distal convoluted tubule Collecting tubule Disease Physiologic Afferent parameter Efferent Sensor Effector Ultrafiltrate Urine.