SF Biology II1 Kidney Function and Regulation
SF Biology II2 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 II3 Functional unit of the kidney
SF Biology II4 Filtration mechanism
SF Biology II5 Functions of the nephron
SF Biology II6 Osmotic gradients
SF Biology II7 Countercurrent multiplier (1/2)
SF Biology II8 Countercurrent multiplier (2/2)
SF Biology II9 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 mosm inside
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SF Biology II12 Renin-Angiotensin — Summary Fall in NaCl, ECF, ABP … JGA release of renin… …catalyses angiotensinogen — AGTI In lungs AGTI — AGTII –…release of vasopressin — H 2 O reabsorption –…arteriolar constriction — reduced renal blood flow –…stimulates thirst — H 2 O intake
SF Biology II13 Renin-Angiotensin — Summary AGTII stimulates adrenal release of aldosterone… –…increased reabsorption of Na renal tubules –… hence H 2 O retained (osmotically) in ECF
SF Biology II14 ADH/vasopressin
SF Biology II15 ?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 II16 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 II17 Urea Recycling — Summary …raising osmotic pressure above tonicity …hence water leaves thin ascending limb (passively) …hence urea is concentrated in ascending limb
SF Biology II18 Urea Recycling — Advantages Increase in medullary tonicity – allows production of hypertonic urine Less water per unit wt of urea excreted Both aid water conservation
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SF Biology II24 Equilibrium