Loop of Henle Flashcards
If albumin gets filtered what happens to it?
completely reabsorbed by Tm mechanism in proximal tubule
What does the liver do to drugs and pollutants to prevent reabsorption?
metabolises them from non polar to polar substances
Why is the fluid leaving the proximal tubule isosmotic with plasma?
all solute movements are accompanied by equal water movement - osmotic equilibrium maintained
What part of the kidney are the proximal and distal tubules found?
cortex
What is a juxtamedullary nephron and what do these contain?
deep to the medulla
loops of henle
What is the main function of the loops of henle
Allow kidney to produce concentrated urine in time of water deficit which is key to survival without water
What is the max urine concentration?
1200-1400mosmoles/l
What is the minimum obligatory water loss per day? Why?
500mls
urea, sulphate, waste and non waste products must be excreted to 600mosmoles
Min concentration of urine
30-50mOsmoles/l
Why can the kidneys produce urine of various concentrations (what does the loop of henle act as?)
counter-current multiplier
What does the ascending limb transport?
actively transport NaCl and Cl out of lumen and into interstitium
impermeable to water
What does the descending limb allow movement of?
water freely
impermeable to NaCl
What happens in the ascending limb to start of the process of the loop of henle?
NaCl pumped out into interstitium which drops the concentration of the lumen but interstitium increases
occurs until limiting gradient
What is the limiting gradient of NaCl transport from ascending limb?
200mosmoles/l
Due to the ascending limb pumping out NaCl what happens to descending limb?
exposed to greater osmolarity in interstitium and H20 moves out of descending limb to equilibrate
What happens to the water which moves out of the descending limb?
high oncotic pressure and tissue P - reabsorbed into the vasa recta
Is the fluid in loops of henle progressively concentrated or diluted in the ascending and descending limb?
concentrated - descending
diluted - ascending
What happens to the interstitium concentration following the ascending and descending limb?
becomes more concentrated due to addition of salt from ascending limb
What is the maximum difference in concentration gradient at any horizontal level between ascending limb and interstitium?
200mOsmol
What does the vertical gradient in interstitium range from?
300-1200mOsmol
If furesmide (loop diuretic) is used that blocks active transport of NaCl from ascending limb what happens to urine?
isotonic
How does the ascending limb re-dilute the fluid in the lumen?
removing NaCl
not by removing water
Is fluid entering distal tubule more or less concentrated than plasma?
less –> more dilute (hypotonic)
What is the overwhelming significance of the counter-current multiplier achieved?
increasingly concentrated gradient in interstitium
What concentration does fluid enter and leave loops of henle?
300mosmol
100mosmol
What are the vasa recta?
special arrangement of peritubular capillaries allows them to do countercurrent exchanges
Why do vasa recta not interfere with interstitial gradient?
arranged in hairpin loops
slow flow
What are vasa recta permeable to and significance of this
water and solutes
equilibrate with medullary interstitial gradient
3 main functions of vasa recta
supply oxygen for medulla
in providing oxygen must not disturb gradient
removes volume from interstitium
What is the flow rate in vasa recta and significance of this
very slow - plenty time for equilibration with interstitium
ensures medullary gradient not disturbed
Where is the site of water regulation?
collecting duct
What is the permeability of collecting duct under control of?
ADH
