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Renal Phys 7

WVSOM -- Renal Phys -- Concentration and Dilution of urine

What is countercurrent multiplication? a process which dilutes loop fluid and at the same time concentrates the medullary interstitum.
What is coutner current exchange? process in the looped vasa recta tha protects the osmotic gradient in the medulla
What are the key concepts about countercurrent multiplication? concentrates loop fluid and reilutes the fluid. Processes a dilute urine to the distal tubule. Creates a concentrated medullary interstitium thru wich the collecting ducts run.
What is the point of final concentration or dilution? collecting ducts
How does osmolality incrase or decrease horizontally across the medulary? it doesn’t
How does osmolatlity change from outer to inner medulla? increasingosmolaity as you go deeper.
Where does ADH act from? Initial collecting tubule to inner medullary collecting duct.
What is the osmolality of the cortical interstitium? same as plasma
What is the corticomedullary osmolality gradient? becomes increasingly hyperosmotic as you descend into the medulla
What happens when someone has been on restricted water intake? ADH is secreted. H3O flows out of collecting tubules and urine becomes concentrated with decreased urea permeability.
What happens to urine in the TAL with a patient on loop diuretics? urine doesn’t get diluted
What happens to the interstitium in a patient on a loop diuretic? does not get concentrated.
What happens to distal nephrons in patients on loop diuretic? increased delivery of Na and solutes that prevent H2O reabsorption
What happens to H2O in the descending limb in a patient on a loop diuretic? decreased reabsoprtion
What happens to urine in a patient on loop diuretics? urine becomes isomotic
What happens to a person who is a victum of water loading? low levels of ADH, low H2O permeability in CT on down, excrete a dilute urine and a low urea permeability
What will create an increasing osmolatity in the medulla? NaCl and Urea
What happens to urea concentrations as you travel thru the medulla? urea concentration rises steeply from the middle of the outer medulla to the pailla
What does urea concentrations rise in the medulla? due to the unique water and urea permeabilities of the collecting tubules and ducts
What will stimulate urea transporters in the medulla? ADH
Where is urea reabsorbed and how much? half reabsorbed in the PT
Where is urea secreted? thick loop of loop of henle to the medullary collecting duct
What determins medullary osmolality? half due to urea and half due to NaCl
Urea transport depends on _______________ differences concentration
What happens at low urine flows? more water has time to be reabsorbed thus leaving lots of urea in the tubule to set upa concentration difference. More UREA is reabsorbed
What happens to urea at high flows? less urea is reabsorbed because more water is swept downstream and less is reabsorbed
What happens in renal disease? low GFR which leads to low urine flow, increase in urea retention and increased BUN
What happens to urin with a low protein intake? Greatly reduced metabolic production of urea and the patient will have a compromised ability to produce concentrated urine
What happens to urine with dehydration? GFR is low and ADH is high so more water is removed from the tubule resulting in a more concentrated medullary intstition due to ADH causing a stimulating urea reabsorption
What happens to urine in diabetes insipidious? patienst have polyuria and poly disia due to low ADH
What is central Diabetes Insipidous? failure of ADH secretion
What is nephrogenic diabetes insipidous? Kidneys respond inadequately to ADH
What is SIADH? syndrom of inappropriate ADH
What happens to urine in SIADH? patients re-absorbe lots of water so urine becomes a lot more concentrated and the plasma na concentration goes down (hyponatremia)
Describe the vasa recta low blood flow with descending and aswcending limbs that run near each other in parallel
Describe solute and water movement in the vasa recta can enter and leave BUT there is no capacity for active transport
What happens to osmolaltiy in the vasa recta? increases as it passes deeper.
Does countercurrent exchange in the vasa recta establish a medullary osmotic gradient? no, instead it keep the gradient created by the countercurrent multiplication from dissipating
Created by: tjamrose