Loop of henle

Question 1

What state does urine enter loop of henle?

Answer 1

Isotonic

Question 2

Function of loop of henle? (3)

Answer 2

1) Na+ reabsorption
2) Urinary dilution
3) Generate medullary hyperosmoticity- allow water diffuse in descending and collecting duct

Question 3

What does descending loop do?

Answer 3

Water permeable
Impermeable solutes

Question 4

What does ascending loop do?

Answer 4

Water impermeable
Permeable solutes

Question 5

Where is water absorbed in loop of henle?

Answer 5

Descending limb

Question 6

Where are solutes absorbed in loop of henle?

Answer 6

Ascending limb

Question 7

Function of descending limb (explain conc change)?

Answer 7

1) Descending limb permeable to water
2) Water flows out due to osmotic pressure
3) Fluid moves down loop it gets more concentrated

Question 8

Why does water flow out of descending limb?

Answer 8

Due osmotic pressure

Question 9

Does fluid become more or less concentrated as goes down descending?

Answer 9

More
Lose water

Question 10

Does fluid become more or less concentrated as goes down descending?

Answer 10

More
Lose water

Question 11

Explain what occurs in thick ascending limb?

Answer 11

1) Na+ reabsorbed (move out) by Na/K ATPase in basolateral membranes
2) Allows further uptake Na+ by NKCC2
Use gradient (secondary active transport) and pump Na+ out of
tubule lumen
K+ recycled on apical membrane back through lumen (ROMK
channels)
3) Cl- leaves cells through CLCK A channels on basolateral
membrane
4) Negatively charged lumen created- repels Ca2+ etc as move
paracellularly
5) Hyperosmotic interstitium created- aid water uptake

Question 12

What is function thin ascending limb?

Answer 12

Salt pumped passively

Question 13

What are 2 ways which Na+ taken up in ascending limb?

Answer 13

1) Na/K ATPase in basolateral membranes
2) NKCC2 uses the gradient (secondary active transport)
Pumps Na+ out lumen of tubule

Question 14

What is process that NKCC2 pump use?

Answer 14

Secondary active transport

Question 15

How is K+ recycled?
Where?

Answer 15

Apical membrane
ROMK channels

Question 16

How does Cl- leave cell?

Answer 16

CLK channels on basolateral membranes

Question 17

Is the tubule positive or negative charged?

Answer 17

Negative charged- repel Ca2+ and Na+

Question 18

What does counter current system result in?

Answer 18

Hyperosmotic interstitium
Low water concentration

Question 19

In ascending limb does tubule become hypo or hyper osmotic?

Answer 19

Hyposmotic

Question 20

What system is used in outermedulla to ensure water and solute reabsorption?

Answer 20

Counter-current system

Question 21

What is function of urea? (explain)

Answer 21

Important inner medulla
1) Vasopressin makes collecting duct permeable to urea
2) Urea moves out of collecting tubule into interstitium
3) Urea is osmotically active and trapped in the interstitium
4) Water drawn down conc. gradient to low water conc (gen by urea)
5) Aids urine concentration in the loop of Henle
6) Urea reabsorbed, secreted into tubule and reabsorbed again
7) Urea freely filtered in the glomerulus- 50% of filtered urea is reabsorbed in proximal tubule, remaining 50% enters the loop of Henle

Question 22

Main function urea?

Answer 22

Create low water conc in intersitium- draws out water

Question 23

What blood supply to glomerulus?

Answer 23

Vasa recta

Question 24

Function of vasa recta?

Answer 24

Ensure counter current gradient maintained
Supply O2 to deep structures

Question 25

Explain how the vasa recta works?

Answer 25

1) Blood moves down descending vasa recta - low solute conc
Solutes move into blood (Na+), water out
Blood more conc
Blood high oncotic pressure- proteins not filtered
By bottom has high solute conc
2) Ascending limb vasa recta water moves from high to low conc
Water moves into vasa recta and is removed
Solutes secreted

Question 26

Why is vasa recta a loop?

Answer 26

Minimise loss of solute by diffusion- maintain gradient

Question 27

Why is vasa recta hairpin?

Answer 27

Slow rate blood flow- maintain osmotic grad required water reabsorption

Question 28

What process do solutes and water move into vasa recta?

Answer 28

Passive diffusion

Question 29

What does countercurrent system maintian?

Answer 29

Conc gradient

Question 30

What maintains counter current system?

Answer 30

Selective permeability in the loops of Henle
Passive diffusion in the vasa recta