Renal Phys 3

• tubular reabsorption


  table:
• filtered loads are big or small

  hella big
• what percent of the filtered volume is reabsorbed?

  99%
• almost complete reabsorption

  water, ions, nutrients, etc.
• incomplete reabsorption; excreted


  wastes
• modes of tubular reabsorption

  1.) diffusion of lipid-soluble substances that don't need carriers

  2.) mediated transport of large/charged substances (ex: glucose)

  
• routes of tubular reabsorption

  transcellular transport and paracellular transport
• apical (luminal) membrane -> basolateral membrane -> renal interstitial fluid -> peritubular capillaries

  transcellular transport
• tight junctions -> renal interstitial fluid -> peritubular capillaries

  paracellular transport
• reabsorption keeps up with filtration at ___ plasma solute concentrations

  low
• solute will be excreted in urine at ____ plasma concentrations if filtration continues but reabsorption has reached its transport _______.

  high; maximum
• when FL > 375,

  you no longer can reabsorb all of that glucose
• when does excretion become linear?

  when nephrons are maxed out
• foreign chemicals, drugs, toxins, hormones, breakdown products, organic wastes, K+, and H+

  secreted during tubular secretion
• diffusion can occur, but usually involves active transport (coupled to Na+ reabsorption)


  during tubular secretion
• transcellular and paracellular routes are in opposite direction as tubular reabsorption

  during tubular secretion
• most secretion occurs into the proximal tubules (except K+ and H+ are mainly secreted into cortical collecting duct)


  during tubular secretion
• secreted substances can have a transport max 


  during tubular secretion
• transport maximum for secreted substances


  graph: