kidneys - virgo32

[ArchivalUser]

please explain countercurrent multiplication and countercurrent mechanisms?

[ArchivalUser]

please explain

[ArchivalUser]

It would be hard to exp w/out img or figure.
But lets try with help of your imagination. 1st step salt/NaCl need to exit in thin by passive diffusion & as it goes higher up by pumped out via Na/k/2Cl cotransport -> H2O stay behind & osmolarity of thick Ascending ↓ 200 ( Na-> interstitial fluid; osmolarity shot up ) create 200 difference btw ascending & interstitial. That difference create mismatch. Water then diffuses out thin descending -> UNTIL equilibrate with interstitial. Once descending equilibrated, 300 fluid from PCT rush top of descending limb. This push the higher osmolarity fluid below down toward hairpin curve -> LOH. Again osmolarities of descending & interstitium are mismatched. That causes H2O leave descending till two fluid re equilibrated. The corticopupillary gradient come to light that (cortex osmolarity 300 & papillary interstitial 400). Two steps repeated with each cycle enhance the gradient; again; salt leaves ascending for interstitial (↓osmolarity of ascending) -> ↑ osmolarity in interstitial -> again as I descried water diffuses out of descending -> ↑ osmolarity in descending till equilibrate interstitial. Low osmolarity from PCT pushes higher osmolarity fluid below it down toward the bottom of LOH. Water again diffuses of descending limb to ↓ interstitial osmolarity & res equilibrate. At max the gradient reach btw cortex & inner medulla. The pic just painted countercurrent multiplication; “Countercurrent”/filtrate flow in opposite directions. In the LOH & “multiplication”/countercurrent flow enables the effects gradient to be INC, i.e multiplied

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Lets try Q, make sure my ATP not wasted in conceptual area.

The ability of the kidney to excrete concentrated urine will ↑ if;

a) The reabsorption of Na by the proximal tubule ↓
b) The permeability of the collecting duct to water ↑
c) The activity of the Na/K pump in the loop of Henle ↓
d) The glomerular capillary P ↑
e) The flow of filtrate through the loop of Henle ↑

[ArchivalUser]

in ascending nacl is permeable but water is not, so nacl moves to intersitium that decrese osmloarity of ascending. opposite is for descending. right? that create gradient called countercurrent multiplication. if i'm wrong sorry but its so confusing ur question is how concentrated urine eill increase > so i think if we decrease the reabsorption of ssodium it increase osmolarity and make it more concentrated. and i'm confusesd if increase permeability of collecting it conserves water and make it concentrated. pleases correct me.

[ArchivalUser]

Ans *E* take look at animation here to get big picture https://www.youtube.com/watch?v=AOqIlrQhqHQ to understand what guyton exp for the Q.

The "countercurrent multiplier" enables the kidney to excrete concentrated urine by increasing the tonicity of the medullary interstitium. If the water permeability of the collecting ducts is increased, the fluid flowing through the collecting ducts reaches osmotic equilibrium with the high tonicity of the medullary intestinum resulting in the excretion of concentrated urine. Anything that reduces the ability of the countercurrent multiplier to increase the tonicity of the medullary interstitium, such as increasing the flow of fluid through the loop of Henle or decreasing the activity of the Na-K pump in the thick ascending limb, will decrease the ability of the kidney to excrete a concentrated urine. Increasing the glomerular capillary pressure increases the GFR and makes it more difficult for the kidney to excrete concentrated urine.

That’s correct for your 1st sentence, but that’s only basic one you should know to understand the sophisticated pic to conserve H2O.
If you recall the PCT has osmolarity of 300 same as area interstitial (isoosmotic). As I explain in the loop, the story it’s different.

Thick Ascending limb, Na pump out & NEG ion/Cl follow -> make the medulla SALTY.
At same time H2O leaves passively from thin Descending limb bz (As you pee in in bathroom in night if u forget to flush & in morning you realize your pee in bottom and water of toilet bowl stand it top of it) Same here surrounding of descending as you go deeper it get more salty -> saltier-> saltiest in the down bottom of hairpin) Again, I don’t wanna lose you. Water leaves passively from thin descending because surrounding area salty land & as water leaves the descending pipe become more concentrated. Now, here you miss point, I didn’t paint in pic assuming you know it and that is; because water move passively out CD due to that salty medulla add to major reason why water move out of collecting duct & reabsorbed back -> back to blood thus leave behind more conc pee!

Read my above exp and try to keep the cycle that;
Single effect/salt reab-> flow of fluid -> signle effect -> flow of fluid & on & on... 39 to 40 times.