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Kidney Function and Regulation

Kidney Function and Regulation. Renal Filtration. Total body water ~40 litres; Plasma Vol. ~3 litres). Filter ~180 litres/day Daily urine vol. ~ l.5 litres. Hence conclude that ~95% is re-absorbed, i.e. conserved. Functional unit of the kidney. Filtration mechanism.

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Kidney Function and Regulation

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  1. Kidney Function and Regulation SF Biology II

  2. Renal Filtration • Total body water ~40 litres; • Plasma Vol. ~3 litres). • Filter ~180 litres/day • Daily urine vol. ~ l.5 litres. • Hence conclude that ~95% is re-absorbed, i.e. conserved. SF Biology II

  3. Functional unit of the kidney SF Biology II

  4. Filtration mechanism SF Biology II

  5. Functions of the nephron SF Biology II

  6. Osmotic gradients SF Biology II

  7. Countercurrent multiplier (1/2) SF Biology II

  8. Countercurrent multiplier (2/2) SF Biology II

  9. Renal Concentration Mechanism — Summary • Loop of Henle as countercurrent multiplier • Ascending limb actively extrudes Na+, K+ • Hence gradient between limbs (200 mosm) • AND vertical gradient in medulla • 300 mosm outside - 1200 mosm inside SF Biology II

  10. SF Biology II

  11. SF Biology II

  12. Renin-Angiotensin — Summary • Fall in NaCl, ECF, ABP … • JGA release of renin… • …catalyses angiotensinogen — AGTI • In lungs AGTI — AGTII • …release of vasopressin — H2O reabsorption • …arteriolar constriction — reduced renal blood flow • …stimulates thirst — H2O intake SF Biology II

  13. Renin-Angiotensin — Summary • AGTII stimulates adrenal release of aldosterone… • …increased reabsorption of Na+ @ renal tubules • … hence H2O retained (osmotically) in ECF SF Biology II

  14. ADH/vasopressin SF Biology II

  15. ?Possible Examination Topics • Pattern/regulation of gut motility • Pancreatic secretion of bicarbonate/enzymes • Digestion/absorption of CHO (vs?) fat • Forces involved in glomerular filtration • autoregulation • Role of urea in hypertonicity of medulla • Basic renin-AGT-aldosterone mechanism • effects on tubular reabsorption SF Biology II

  16. Urea Recycling — Summary • Distal tubule and early collecting tubule • NOT permeable to urea or water* • *Vasopressin allow water to move passively • …hence urea is concentrated. • Distal collecting tubule IS permeable to urea • …hence urea diffuses into interstitium… SF Biology II

  17. Urea Recycling — Summary • …raising osmotic pressure above tonicity • …hence water leaves thin ascending limb (passively) • …hence urea is concentrated in ascending limb SF Biology II

  18. Urea Recycling — Advantages • Increase in medullary tonicity • allows production of hypertonic urine • Less water per unit wt of urea excreted • Both aid water conservation SF Biology II

  19. SF Biology II

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  24. Equilibrium SF Biology II

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