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Human Anatomy and Physiology

Human Anatomy and Physiology. Renal function. Functions. Regulation of water and electrolytes Maintain plasma volume Acid-base balance Eliminate metabolic wastes Hormone secretion. Kidney anatomy. Anatomy. Functional unit is the nephron Components Glomerulus Proximal tubule

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Human Anatomy and Physiology

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  1. Human Anatomy and Physiology Renal function

  2. Functions • Regulation of water and electrolytes • Maintain plasma volume • Acid-base balance • Eliminate metabolic wastes • Hormone secretion

  3. Kidney anatomy

  4. Anatomy • Functional unit is the nephron • Components • Glomerulus • Proximal tubule • Loop of Henle • Distal tubule • Common Collecting duct

  5. Nephron anatomy • Nephron types • Juxtamedullary • Cortical • Peritubular capillaries • Vasa recta

  6. Renal processes • Filtration • Water and solutes • Protein (Not filtered) • Blood cells (No filtered) • Filtration based onsize and charge

  7. Glomerular Filtration Size barrier Size barrier

  8. Glomerular Filtration

  9. Renal processes • Reabsorption • 99% of water & solutes • Passive - water • Active - sodium • Proximal tubule (65%)

  10. Reabsorption at cell level • Sodium moves passively across the apical membrane and actively into the plasma

  11. Renal processes • Secretion • Water and solutes (1%)

  12. Secretion at cell level • Potassium is transported actively into the cell and passively into the tubular lumen

  13. Urine formation • Volume of fluid into kidneys per day 1,640 L • Volume filtered into the glomeruli per day 180 L • Volume of fluid excreted/day ~ 1.5L • Hence 180 - 178.5 L = amount reabsorbed (~99%)

  14. Blood supply • GFR will depend on blood supply • Blood pressure drop in the glomeruli

  15. Glomerular filtration • Total amount of filtrate formed per minute • Influenced by: • Filtration surface area • Filtration membrane permeability • Net filtration pressure

  16. Glomerular filtration • Measured by a marker • Characteristics • Freely filtered by the glomerulus • Not reabsorbed or secreted • Must not alter GFR

  17. Glomerular filtration • Inulin • Renal clearance • GFR x P(In) = U(In) x V

  18. Regulation of GFR • 3 mechanisms • Renal autoregulation • Neural control • Renin-angiotension system(JG apparatus)

  19. JG apparatus

  20. Regulation of GFR

  21. Countercurrent multiplication 65% 14% 15% 5%

  22. Urea

  23. Urine concentration • Vasopressin: antidiuretic hormone (ADH) • Posterior pituitary, increases the number of aquaporin water channels in the CD

  24. Vasa recta • Osmotic gradient not washed out • Blood supply sluggish • Medulla blood flow is 2% of that to the kidneys

  25. Urine concentration • The urine to plasma osmolality ratio • [U]/[P] • Plasma osmolality from 285 - 295 mOsm • Example: [urine] = 1,200 mOsm, ratio = 4.0

  26. Urine dilution

  27. Urine dilution • Atrial natriuretic peptide (ANP) • Atrium of the heart, decreases Na+ and water reabsorption ADH/ANP ADH/ANP

  28. Diuretics • Action of Diuretics • Alcohol: inhibits ADH • Caffeine: promotes renal vasodilation, increasing GFR • Drugs: any that inhibit sodium reabsorption

  29. Micturition • Mechanism of action • Contraction of detrusor muscle • Relaxation of sphincters

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