what exactly is secretion?

[foofighter7]

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im having difficult with this. I understand filtration, excretion and reabsoption, but I don't get what secretion means?

in first aid it says, secretion=excretion-filtered

 

[dermbaby]

i think, Secretion = NET excretion..

 

[Ty Webb]

i think, Secretion = NET excretion..

This is incorrect.

Just as tubular cells can reabsorb solutes from the tubular fluid they can also secrete solutes into the tubular fluid. This is called secretion and is responsible for things such as potassium loss in a hyperaldosterone state.

Per the equation you provided, whatever amount of solute that is excreted but that wasn't originally filtered through the glomerulus must have been secreted in the nephron (across the peritubular capillaries into the tubular cells and then into the tubular fluid).

Hope this helps.

 

[ArcGurren]

filtration = all the stuff that is filtered out through the glomerulus
reabsorption = all the stuff that goes from the nephron tubules back into the blood stream/interstitial tissue
secretion = extra stuff is secreted from the blood into the tubules at various points in the nephron. the best example of this is PAH.