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Physiology of the Kidneys Body Fluids & Acid Base Balance

Physiology of the Kidneys Body Fluids & Acid Base Balance. John R. Dietz Physiology & Biophysics University of South Florida College of Medicine. MDC 3538 974-1548 jdietz@hsc.usf.edu. arquivo extraído gratuitamente de: http://www.biosciednet.org/portal/ recomendado pela APS

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Physiology of the Kidneys Body Fluids & Acid Base Balance

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  1. Physiology of the Kidneys Body Fluids & Acid Base Balance John R. Dietz Physiology & Biophysics University of South Florida College of Medicine MDC 3538 974-1548 jdietz@hsc.usf.edu

  2. arquivo extraído gratuitamente de: http://www.biosciednet.org/portal/ recomendado pela APS Veja animações, aulas ppt e outros em:

  3. Body Fluid Compartments & Physiological Solutions By John R. Dietz, Ph.D. Physiology & Biophysics University of South Florida College of Medicine

  4. THREE EMERGENCY ROOM PATIENTS • 80 year old male with AD - over medicated because of • irritability and has had nothing to drink for 3 days. • 3 week old infant with vomiting and diarrhea • for 2 days. • Gunshot wound - loss of 2 liters of blood.

  5. BODY FLUIDS DISTRIBUTION: Total body water (TBW) varies from 50-70% of body weight (ave. = 60%). In an average person (70Kg) this is: 0.6 X 70Kg = 42Kg or 42L

  6. PERCENTAGE OF WATER IN TISSUES

  7. Intracellular (ICF): 40% of Bd. Wt. 28L Extracellular (ECF): 20% of Bd. Wt. 14L Plasma: 4-5% of Bd. Wt. 20% of ECF

  8. MEASURING THE SIZE OF COMPARTMENTS

  9. Molar and Equivalent Concentrations

  10. Osmolality Osmolality: millimoles of solute/Kg of H2O; Osmolarity: millimoles of solute/L of H2O Activity of H2O decreases as Osmolality increases. Colligative Properties of Solutions: Depend on number of molecules and not on their nature. • Boiling Point • Freezing Point • Vapor Pressure • Osmotic Pressure A B

  11. APPROXIMATE IONIC COMPOSITION OF THE BODY WATER COMPARTMENTS

  12. Comparison of the Three Major Compartments Capillary Interstitium Intracellular Permeable to most solutes but imperm- eable to large proteins Impermeable to most solutes Na+ 140 mM Na+ 142 mM Na+ 10 mM K+ 4.5 mM K+ 4.5 mM K+ 140 mM Proteins 1.5 mM Proteins 0.1 mM Proteins 3 mM Pc = 25 mmHg P = 0 mmHg = 28 mmHg = 3 mmHg Osm. = 286.5 mOsm/L 285 mOsm/L 285 mOsm/L Colloid Osmotic Pressure, Protein Osmotic Pressure, Oncotic Pressure

  13. CHANGES IN BODY FLUID COMPARTMENT VOLUMES

  14. “The total body content of sodium is the principal determinant of extracellular and intravascular fluid volume” • Na+ & anions – Extracellular • K+ & anions – Intracellular • D5W = Water – adds no effective osmoles • At equilibrium, osmolality is the same in all compartments • Calculate TBW first, the ECF and ICF

  15. Addition of 1 L of H2O

  16. Add 1 L of normal saline (0.9%) or 0.150M or 150 mM or 300 mOsm/L

  17. Problem We infuse 2 Liters of a 0.45% solution of NaCl. How many total osmoles have we infused? What is the new osmolality after infusion?

  18. Add 2 Liter of Half-Normal Saline (0.45%) TBW ECF ICF

  19. Add 2 Liter of Half-Normal Saline (0.45%) TBW ECF ICF 0.075M NaCl = 75 mM Na+ & 75 mM Cl- but 2 L so there are 300 mOsm total added as a hypotonic solution

  20. Add 2 Liter of Half-Normal Saline (0.45%) TBW ECF ICF

  21. Add 2 Liter of Half-Normal Saline (0.45%) TBW ECF ICF

  22. Add 2 Liter of Half-Normal Saline (0.45%) TBW ECF ICF

  23. Add 2 Liter of Half-Normal Saline (0.45%) TBW ECF ICF

  24. Problem What would you expect to happen to fluid compartments if we infuse KCl?

  25. Fluids Commonly Lost

  26. LOSS OF GI FLUIDS

  27. PATHOPHYSIOLOGICAL CHANGES IN EXTRACELLULAR FLUID VOLUME Volume Contraction Isotonic Hypertonic Hypotonic Osmolality ECF ECF ECF ICF ICF ICF Volume Expansion Isotonic Hypertonic Hypotonic Osmolality ECF ECF ECF ICF ICF ICF From H. Valtin Program

  28. THREE EMERGENCY ROOM PATIENTS • 80 year old male with AD - over medicated because of • irritability and has had nothing to drink for 3 days. • 3 week old infant with vomiting and diarrhea • for 2 days. • Gunshot wound - loss of 2 liters of blood.

  29. Glomerular Filtration By John R. Dietz, Ph.D. Physiology & Biophysics University of South Florida, College of Medicine

  30. Renal Failure Patient

  31. FUNCTIONS OF THE KIDNEYS • Remove wastes. • Reg. Vol. and Composition of ECF. • Acid-Base Balance. • Blood Pressure Regulation. • Removal of Foreign Substances. • RBC Production. • Vitamin D Activity.

  32. Early Proximal Tubule Distal Tubule Cortical Late Thick ascending (diluting segment) Collecting Duct Thin descending Thin ascending Medullary Loop of Henle

  33. Efferent Arteriole Afferent Arteriole Blood Supply to the Kidneys Note the 3 capillary beds: • Glomerular capillaries • Peritubular capillaries • Vasa recta

  34. Innervation of the Kidneys Sympathetic • Afferent & Efferent Arterioles • Juxtaglomerular cells • Tubule

  35. Filtration Secretion Excretion Reabsorption Basic Theory of Urine Formation

  36. Glomerular Filtration Production of a protein - free filtrate of plasma

  37. THE GLOMERULAR MEMBRANE Three Sieves in Series • Capillary Endothelium • Basement Membrane • Bowman’s Capsule Epithelium • (podocytes)

  38. Permeability Based on Molecular Size

  39. Permeability Based on Charge

  40. Starling Forces for Skeletal Muscle Capillary PC 32 pC 25 25 mmHg Blood Flow 15 mmHg PT 1 mmHg pT 2mmHg

  41. Starling Forces Across the Glomerular Capillary PGC 50 45 mmHg Blood Flow 35 mmHg pGC 25 PBC 10 mmHg pBC0mmHg GFR = 125 ml/min = 180 L/day NFP = 8-10 mmHg outward

  42. Regulation of Glomerular Filtration

  43. Regulation of GFR • Changes in Kf (Permeability or • Surface area): • Mesangial Cell Contraction or Relaxation • + ANP, NO • - AII, Endothelin, Norepi, • Epi, ADH

  44. Clearance A volume of plasma from which a substance is completely removed by the kidneys per unit time. Cx = UF  Ux = Volume/Time eg. ml/min or L/day Px Where UF = urine flow; Ux = urine concentration of X; Px = plasma concentration of X; Cx = clearance of X

  45. Measurement of GFR (Inulin M.W. = 5,000) Freely Filtered Not Metabolized Not Reabsorbed Does Not Change GFR Not Secreted Not Produced Amount Filtered = Amount Excreted GFR · PIN = UF ·UIN GFR = UF ·UIN = CIN PIN

  46. Inulin in the Kidney RPF = 600 RPF = 475 Glomerulus I = I = 1 Renal Artery GFR = 125 I = Vasa Recta Capillaries Peritubular Capillaries RPF = 60 RPF = 415 Salts & Water Reabsorbed but no Inulin Reabsorbed Salts & Water Reabsorbed but no Inulin Reabsorbed RPF = 599 I = Renal Vein (All flows are in ml/min) (I = Inulin concentration in mg/dl) Urine Flow = 1 - 5 I = 50 -100 ? 1 ? 1 0.8 ?

  47. Changes in Plasma Creatinine in Renal Failure

  48. Compensatory Hypertrophy • 1) Changes in GFR • a. Disease • b. Transplantation • 2) Changes in GFR with age

  49. Changes in GFR in Chronic Renal Disease

  50. Daily Creatinine Excretion • Varies based on weight & gender • Equals creatinine production • May be normal even in chronic renal failure GFR = UF ·Ucreatinine (Creatinine Excretion) PCreatinine

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