Loop of henle Flashcards
Fluid that is filtered through the glomerular capillaries into the proximal tubule is … with plasma at what conc.
isosmotic
300mOsmoles/l
Max conc. of urine that can be produced by kidney
1200-1400mOsmoles = 4x conc. of plasma (lots of excess solute over water)
urea, sulphate, phosphate, other waste products and non-waste ions (Na+ and K+ ) which must be excreted each day amount to around how many mOsmoles
this means the minimum H20 that must be excreted daily to excrete these ions is …
around 600
500mls
Kidneys contain 2 types of nephrons (superficial cortical and juxtamedullary nephrons)
Although both cortical and juxtamedullary nephrons regulate the concentrations of solutes and water in the blood, which of these is more involved in developing the osmotic gradients that are needed to concentrate urine
juxtamedullary
The loops of henle of juxtamedullary nephrons act as
counter-current multipliers
2 essential features of the loops of Henle which enable them to act as countercurrent multipliers
Ascending limb is permeable to solutes but impermeable to water due to lack of aquaporin actively co-transports Na+ and Cl- ions out of the tubule lumen into the medullary interstitium
Descending limb freely permeable to water due to lots of aquaporin but impermeable to solutes
Since the ascending limb is permeable to solutes but impermeable to water due to lack of aquaporin, what effect does this have on the tonicity of the ascending limb and the tonicity of the medullary interstitium
makes filtrate hypotonic - less salty
makes medullary intersitium hypertonic - more salty
Descending limb is freely permeable to water but what actually drives the movement of water into the medullary interstitium
The active transport of Na+ and Cl- ions from the ascending limb into the medullary intersitium, since that will be more salty it attracts water into the interstitium to dilute it
Since the descending limb is freely permeable to water due to lots of aquaporin, what effect does this have on the tonicity of the descending limb and the tonicity of the medullary interstitium
makes descending limb more hypertonic - more salty
makes medullary interstitium hypotonic - less salty
What does a countercurrent mechanism system mean
mechanism that expends energy to create a concentration gradient
As NaCl is pumped out of the ascending limb, its concentration falls and that of the interstitium rises.
This occurs until the max conc/ of the medullary interstitium is reached and limiting gradient of how many mOsmoles is stabilised
200
The most key step in the loop of henle is
Active removal of NaCl from ascending limb via active transport into medullary intersitium
Loop of henle is a bit counter-intuitive because it works backwards - expand on this
It’s the active removal of NaCl from ascending limb via active transport into medullary interstitium that exposes the descending limb to a greater osmolarity in the interstitium, createing an osmotic gradient for water removal from the descending limb into the interstitium to equilibrate the osmolarity
but this doesn’t matter because there’s constantly fluid in the nephron
The water that’s reabsorbed into the medullary interstitium from the descending limb doesn’t stay there - what happens to it
reabsorbed by the high oncotic pressure and tissue pressure into the vasa recta
The fluid in the tubule is progressively … as it moves down the descending limb and progressively … as it moves up the ascending limb.
concentrated
diluted
At any horizontal level there is only a … mOsmol gradient between ascending limb and interstitium that sodium is transported AGAINST
200
Where do loop diuretics act on
act at the ascending limb of the loop of Henle
If loop diuretics such are furosemide were used, what effect does this have on the loop of henle
- talk about conc. gradients and tonicity of urine
all concentration gradient differences are lost as loop diuretics inhibit the reabsorption of Na+, Cl- and K+ into the intersitium so no gradients would be established so the kidney would only produce isotonic urine
Fluid enters proximal tubule at … mOsmoles and leaves at … mOsmoles
300
100
the 200 left behind concentrates the intersitium
What is the vasa recta
Specialised peritubular capillaries that are a continuation of the efferent arterioles of specifically the juxtamedullary nephrons of the loop of henle, so follow the direction of the loop of henle
The movement of fluid through the tubules causes the … fluid to move further down the loop
Repeating many cycles causes fluid to be near … at the top of Henle’s loop and very … at the bottom of the loop
hyperosmolar
isoosmolar
concentrated
In the outer two-thirds of the renal cortex, the efferent arterioles form what is a known as a … network, supplying the nephron tubules with … and …
The inner third of the cortex and the medulla are supplied by long, straight arteries called … …
peritubular
oxygen and nutrients
vasa recta
If renal medullary capillaries drained straight through the loop of henle, what would they destroy
wash away the conc. gradient that’s been achieved in the medulla by trying to remove the NaCl that’s been concentrated in the medulla
How does the arrangement of the vasa recta prevent the medullary interstitial gradient from being destructed
keeps the NaCl pumped out from the ascending limb to stay in the medullary interstitium
and the water moved out from the descending limb to be removed by the vasa recta
so constantly maintaining that concentrated medullary interstitium
The vasa recta is important for what process
countercurrent exchange
What is the purpose of countercurrent exchange by the vasa recta
to maintain hypertonicity of the renal medulla
How does the vasa recta act as a countercurrent exchanger
On the descending portion of the vasa recta, NaCl and urea are reabsorbed into the blood, while water is secreted.
On the ascending portion, NaCl and urea are secreted into the interstitium, while water is reabsorbed
What drives water movement into the vasa recta
High oncotic pressure because vasa recta is impermeable to plasma proteins so driving water movement from interstitium into the vasa recta
Functions of the vasa recta (2)
Provide oxygen and nutrients for medulla
Removes water from interstitium to keep it concentrated
