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MCB 135E Discussion

MCB 135E Discussion. MIDTERM II Review. Monday the 7 th of November 2040 VLSB 6-8pm E-mail questions regarding exam well in advance. The Kidney and Urinary System. Anatomy Function Hormones Circulation Development. Kidney Functions. Regulates Water Electrolyte balance pH Removes

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MCB 135E Discussion

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  1. MCB 135E Discussion

  2. MIDTERM II Review • Monday the 7th of November • 2040 VLSB • 6-8pm • E-mail questions regarding exam well in advance

  3. The Kidney and Urinary System • Anatomy • Function • Hormones • Circulation • Development

  4. Kidney Functions • Regulates • Water • Electrolyte balance • pH • Removes • Waste • Secretes Hormones • Erythropoiten • Renin • Vitamin D3

  5. Metabolic and Excretory Functions • Glomerular Filtration • Selective filtration of blood • Tubular Reabsorption • Takes up some solutes from filtrate and delivers them to peritubular capillaries • Tubular Secretion • Adds some of its own products to the filtrate, passes filtrate on to bladder as urine

  6. Water Metabolism • Osmotic Pressure – • Force driving or pulling a solvent from lesser to greater concentration on either side of a selectively permeable membrane • Regulation of solute exchange • Selective permeability of membrane • Influence of hormones and metabolites on membrane • Simple and exchange diffusion across membrane • Active secretion by the membrane

  7. Acid Base Balance • Determined By: • Hydrogen Ion Concentration (pH) • Normal 7.3-7.5 • Max 7.0-7.8 • Alkali reserve • CO2 combing power of plasma • Normal 50-70% Volume • Both vary due to exercise and metabolism

  8. Acid-Base Regulation • Buffers, Ventilation, Kidney • Buffers • Cellular proteins, phosphate ions, Hemeglobin (Chloride Shift) • Ventilation • Rate and depth of respiration controls CO2 release in lungs • Increased respiration in a respiratory compensation for acidosis • Kidney • Excretes H+ • Reabsorbs HCO3-

  9. Urine Acidification Mechanisms • Reabsorption of Filtered Bicarbonate • In proximal tubule: H+ exchanged for Na+ • In distal tubule and collecting duct • CO2 and HCO3(-) are transported into cell and form H2CO3 by carbonic anhydrase • Dissociation of H2CO3 releases H+ which is then exchanged for Na+ • Secretion of Ammonia • In distal tubule • NH3 + H-  NH4 (Ammonium) [formation of a titrable acid]

  10. Mechanism for Renal Acid/Base Balance • Apical Na(+)/H(+) antiporter • Basolateral Na(+)/HCO3(-) symporter • H(+) ATPase • H(+)/K(+) ATPase • NA(+)/NH4(+) antiporter

  11. Proximal Tubule Acid/Base Balance • H(+) is secreted into the lumen in exchange for Na(+) • Secreted H(+) then combines with the filtered bicarbonate to form CO2 in the lumen • CO2 diffuses into the proximal tubule cell and combines with water to form carbonic acid, this dissociates to form H(+) and HCO3(-) in the cytoplasm (Involves carbonic anhydrase) • The H(+) is secreted again by the antiport in step 1 • The HCO3(-) is transported out of the cell by a NA(+)/HCO3(-) symporter where it can function as a buffer

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