BLOCK III - BLOCK III • Blood that leaves vasa recta is...

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Unformatted text preview: 12/11/10 BLOCK III • Blood that leaves vasa recta is constant in osmolarity – makes sure • Amplification of absorptive capacity of the loop • Works because of asymmetric permeability in two loops of Henle • Start with 300 mOsmol solution; because of absorption and NaCl, osmotic difference is set up between the two limbs 12/11/10 • This works by interaction with Vasa Recta • In a shallow nephron, it might only see 600 at the tip • Water that leaves the loop of Henle in descending part which is pulled by osmolarity in the interstitium is pulled by ascending limb • As NaCl is being reabsorbed to decrease osmolarity, it contributes to maintaining the osmolarity of the interstitium by moving to Vasa recta 12/11/10 • Counter current exchange – two tubes needed; to make sure that there is absorption, osmolarity not washed away and making sure that there is no marked change in osmolarity & contributes to maintaining the loop of Henle’s function • There is a countercurrent exchange in all nephrons but in cortical nephrons, peritubular capillaries are loosely defined so not well organized as medullary nephrons 12/11/10 BLOCK III START • Anything you take in is absorbed with regards to NaCl, only less than 5-10% is excreted • 120 – 5mmol enters the plasma, that partitions into the fluid compartments • Sodium is higher in ECF, low in ICF • ICF has the highest water • Small losses via sweat glands; most goes to kidney • 110mmol dealt in kidney, absorb 110, 12/11/10 • Majority of it is reabsorbed, minor excretion of 100mmol • Thus, high flow rates and reabsorb majority of what is being filtered and then in latter segments, dilute it • Take a human give sodium bolus continuously, in order to prevent continuous volume expansion, first restrict sodium and then increase sodium by 10 folds • What you see is that your sodium output increases to mere increase in 12/11/10 • This happens because of the ability of nephron to compensate water and salt – from regulation of hormone and collecting duct • If you take two nephrons – one in water balance, uvolemia; pair with increased volume – hypervolemia similar to hypernatremia • In one case, you want to conserve water, in other you want to excrete sodium or water 12/11/10 • HYPERVOLEMIC: GFR goes up; in the PT, start saturating some machinery, it will absorb more which is not a perfect compensation; increase amount that is reabsorbing but it is less since there is no perfect balance • Example PT absorbs 50%, loop absorbs more, DT absorbs more, the fluid that is left going to the collecting duct is 80% of the initial filtrate; no ADH, no aldosterone thus majority of it is excreted 12/11/10 MAJOR DETERMINANTS OF SODIUM EXCRETION...
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This note was uploaded on 12/10/2010 for the course PGY 451 taught by Professor Baizer during the Spring '09 term at SUNY Buffalo.

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BLOCK III - BLOCK III • Blood that leaves vasa recta is...

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