Physio 5

Question 1

What is the combination of the opposing flow useful for?

Answer 1

coutnercurrent multiplication –> sets up the corticomedullary concetration gradient –> hypertonic urine

Question 2

Which nephrons have longer loops of henle and vasa recta?

Answer 2

Juxtamedullary nephrons

Question 3

What allows the paracellular reabsorption across proximal tubule?

Answer 3

the leakiness of the proximal tubule

Question 4

What reabsorption occurs in the descending limb of the Henle?

Answer 4

No salt reabsorption

Only water reabsorption

Question 5

What occurs in the ascendling limb of the loop of henle?

Answer 5

Active salt reabsorption

No water reabsorption

Question 6

Why does no water reabsorption occur in the ascending limb?

Answer 6

The tight junctions are tight and not leaky –> hence impoermeable to water absorption

Question 7

Where is the Na/ K tranporter found in the ascending loop?

Answer 7

basolateral membrane

Question 8

Triple cotransporter in the ascending loop

Answer 8

1 Na, 1 K and 2 Cl ions from the tubular fluid into the tubular cells

K recycle back into the tubular fluid

Net flow: Na and Cl from tube into cell, K goes in circles

Question 9

What happens to the K at the apical and basolateral membrane?

Answer 9

Recycling of the fluid

Net movement of the salt from the tube to the interstitial fluid

leaves via a basolateral K channel or along with the Cl ion

Question 10

Where do loop diuretics act?

Answer 10

Act on and inhibit the activity of the triple cotransporters at the ascending limb of the loop of henle

Question 11

What happens to the osmolarity of the interstitial fluid in the ascending limb?

Answer 11

Concentrate the interstitial fluid with salt and the ascending limb becomes dilute

Question 12

What happens to the osmolarity across the loop of henle?

Answer 12

1. Solute removed from lumen of ascending limb (water cannot follow)
2. Tubular fluid is diluted and osmolality of interstitial fluid is raised
3. Interstitial solute cannot enter the descending limb
4. Water leaves the descending limb by osmosis
5. Fluid in the descending limb is concentrated

Question 13

How is the cporticomedullary concentration gradient formed?

Answer 13

As the tubular fluid is made less concentrated and the interstitial fluid is made more concentrated

more concetration of the tubular fluid as it comes down the descending loop and its concentration reduces as it goes up the ascendiong limb

The intersttial fluid has a concentration of 1200 mosmol/L

Question 14

Comment on the concentration of the interstitial fluid in different parts of the kidney

Answer 14

within the cortex the concentration of interstitial fluid is less, but as yoo move down to the medulla the concentration of the interstitial fluid increases

Question 15

What is the 2 solute hypothesis?

Answer 15

Reabsporption of urea –> 2 solute hypothesis

describes the composition of the cortico-medullary concentration gradient:

Question 16

What is the importance of corticomedullary concetration gradient?

Answer 16

Corticomedullary concentration gradient and circulating ADH, enables the kidney to concentrate the medullary interstitial fluid and thereby produce urine of different concentrations and vilume

Question 17

What is the change in the blood osmolarity as it moves through the vasa recta?

Answer 17

No change in the osmolarity of the blood as it moves across the vasa recta

Question 18

Importance of the vasa recta

Answer 18

to maintain the cortico-medullary concentration gradient