Glomerular filtration, tubularReabsorption and tubular Secretion

Glomerular filtration, tubularReabsorption and tubular Secretion

1. Glomerular Filtration

   • 180L/day
     • 125ml/min
   • GFR = Kf x Net filtration pressure (NFP)
     • (NFP) = (PGC – PBS) – (OnGC - OnBS)
     • Kf (filtration coefficient) depends on • the hydraulic conductivity (permeability) of the capillary and • the effective surface area available for filtration.
   • GFR is directly related to blood pressure
   • sympathetic stim DECREASE GFR
   • not a selective process

2. Tubular Reabsorption

   • All except potassium
   • Na+-K- pump and carrier proteins (e.g. glucose transporter or GLUT) always reside on the basolateral membrane.
   • Na+ channels and co-transporter proteins (e.g. Na+-glucose symporter, Na+- amino acid symporter, Na+-Cl- symporter, and Na+-H+ antiporter) are on the apical membrane.
   • diffusion
     • Na+, K+, Cl-, urea in the PCT

3. Morphology of epithelial cells lining various sections of the nephron

4. Reabsorption in the Loop of Henle

   • descending
     • water ONLY
   • ascending
     • Electrolytes

5. Reabsorption in the early Distal Convoluted Tubule (DCT)

   • Ca2+
     • passive transport

6. Reabsorption and Secretion in the Collecting Duct

   • Principal cells reabsorb Na+ and secrete K+
     • target for aldosterone and ADH
   • intercalated cells reabsorb K+ and HCO3-, and secrete H+

7. tubular secretion

   • PCT
     • H+: variable (via Na+-H+ antiporters)
     • NH4+: variable, increase in acidosis (antiporters)
     • Urea: variable (diffusion)
     • Creatinine: small amount
   • thin LoH
     • Urea: variable (recycling from collecting duct)
     • NH4+: variable (recycling from thick ascending loop of Henle)
   • CD
     • K+: variable amount to adjust to dietary intake (via leakage channels of the principle cells)
     • H+: variable amount to maintain acid-base homeostasis (via proton pump)

8. Sites of action of diuretics

9. Summary of basic renal processes

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