Loop of henle

Question 1

Fluid that is filtered through the glomerular capillaries into the proximal tubule is … with plasma at what conc.

Answer 1

isosmotic

300mOsmoles/l

Question 2

Max conc. of urine that can be produced by kidney

Answer 2

1200-1400mOsmoles = 4x conc. of plasma (lots of excess solute over water)

Question 3

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 …

Answer 3

around 600

500mls

Question 4

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

Answer 4

juxtamedullary

Question 5

The loops of henle of juxtamedullary nephrons act as

Answer 5

counter-current multipliers

Question 6

2 essential features of the loops of Henle which enable them to act as countercurrent multipliers

Answer 6

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

Question 7

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

Answer 7

makes filtrate hypotonic - less salty

makes medullary intersitium hypertonic - more salty

Question 8

Descending limb is freely permeable to water but what actually drives the movement of water into the medullary interstitium

Answer 8

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

Question 9

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

Answer 9

makes descending limb more hypertonic - more salty

makes medullary interstitium hypotonic - less salty

Question 10

What does a countercurrent mechanism system mean

Answer 10

mechanism that expends energy to create a concentration gradient

Question 11

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

Answer 11

200

Question 12

The most key step in the loop of henle is

Answer 12

Active removal of NaCl from ascending limb via active transport into medullary intersitium

Question 13

Loop of henle is a bit counter-intuitive because it works backwards - expand on this

Answer 13

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

Question 14

The water that’s reabsorbed into the medullary interstitium from the descending limb doesn’t stay there - what happens to it

Answer 14

reabsorbed by the high oncotic pressure and tissue pressure into the vasa recta

Question 15

The fluid in the tubule is progressively … as it moves down the descending limb and progressively … as it moves up the ascending limb.

Answer 15

concentrated

diluted

Question 16

At any horizontal level there is only a … mOsmol gradient between ascending limb and interstitium that sodium is transported AGAINST

Answer 16

200

Question 17

Where do loop diuretics act on

Answer 17

act at the ascending limb of the loop of Henle

Question 18

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

Answer 18

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

Question 19

Fluid enters proximal tubule at … mOsmoles and leaves at … mOsmoles

Answer 19

300

100

the 200 left behind concentrates the intersitium

Question 20

What is the vasa recta

Answer 20

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

Question 21

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

Answer 21

hyperosmolar

isoosmolar

concentrated

Question 22

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 … …

Answer 22

peritubular

oxygen and nutrients

vasa recta

Question 23

If renal medullary capillaries drained straight through the loop of henle, what would they destroy

Answer 23

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

Question 24

How does the arrangement of the vasa recta prevent the medullary interstitial gradient from being destructed

Answer 24

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

Question 25

The vasa recta is important for what process

Answer 25

countercurrent exchange

Question 26

What is the purpose of countercurrent exchange by the vasa recta

Answer 26

to maintain hypertonicity of the renal medulla

Question 27

How does the vasa recta act as a countercurrent exchanger

Answer 27

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

Question 28

What drives water movement into the vasa recta

Answer 28

High oncotic pressure because vasa recta is impermeable to plasma proteins so driving water movement from interstitium into the vasa recta

Question 29

Functions of the vasa recta (2)

Answer 29

Provide oxygen and nutrients for medulla

Removes water from interstitium to keep it concentrated