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 on size and charge

7. Glomerular Filtration 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% 5% 14% 15%

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. Atrial natriuretic peptide (ANP) Atrium of the heart, decreases Na + and water reabsorption 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