Need help on a kidney concept please!!

[rauljimenez]

---

Members do not see this ad.

Im looking for a way to grasp this concept but I cant get it home , maybe you guys can help me out here it goes :

• The increase in oncotic pressure during a decrease in renal blood flow is what’s responsible for reabsorbing anything into the blood stream from the kidney.


How does the increase in oncotic pressure helps in reabsorbing material out of the proximal tubule guys??

 

[kstreet]

If the oncotic pressure is higher in the peritubular capillaries it can shift more stuff in bc of the higher osmotic gradient.

Imagine if instead the peritubular capillaries were all watery and hypoosmolar, it wouldn't be as effective at taking stuff up from the proximal tubule.

But if the peritubulars are dry as a bone (high oncotic pressure) the plasma proteins are going to suck up more fluid and absorb more stuff.

Remember though, it's always a balance because if the oncotic pressure is way to high, that will probably also lower GFR in the glomerulus. This is because the same forces that let a high oncotic pressure suck up fluid from the peritubular capillaries will also be the same in preventing as much fluid leaving the blood vessel to enter bowmen's space.

 

[jfgavina]

Very difficult concept to understand. If you have more oncotic pressure wouldn't it be counter productive to absorb aminoacids and glucose from the proximal tubule?

 

[bbydoc]

agree with the above.

in regard to the PCT:
as the oncotic pressure from the peritubular capillaries suck fluid in (as mentioned above) Ions can move along paracellularly, this mechanism is called solvent drag. it turns out that the tight junctions are not as tight as I had assumed, and the claudin molecules between cells form channels that are of similar size as the conventional ion channels on the apical surface.

 

[rauljimenez]

Thank you guys, got the concept !!!