L06: Renal Tubular Function 2

Question 1

What structure after the proximal tubule do we get

Answer 1

Loop of henle

Question 2

What is the loop of henle divided into

Answer 2

Descending limb

Ascending limb

Question 3

What is the role of the ascending limb

Answer 3

Create a high osmolarity interstitial space in the medulla so water from the descending and collecting duct is reabsorbed.

Question 4

Which layer is the loop of henle found in

Answer 4

Medulla

Question 5

How is water reabsorbed in the loop of henle

Answer 5

Through the gaps between cells.

Question 6

Which ions are reabsorbed in the thick ascending limb

Answer 6

Sodium
Chloride
Potassium

Question 7

Describe the reabsorption of the sodium, potassium and chloride from the apical membrane through the basolateral membrane into the interstitial space

Answer 7

Apical membrane
1) sodium, potassium and chloride cotransporter called NKC22 brings in sodium,potassium and chloride into the cell.

Basolateral membrane

2) sodium leaves out via the 3na+/2k+ pump
3) potassium leaves via the potassium channels
4) chloride leaves via the chloride channels into the interstitial space

Question 8

Is the thick ascending limb permeable or impermeable to water

Answer 8

Impermeable to water

Question 9

Why is the thick ascending limb impermeable to water (think of how water moves through cells)

Answer 9

The gaps between cells are blocked so water can pass through the gaps.

Question 10

What is furosemide

Answer 10

Diruetic

Question 11

What is the role of a diuretic

Answer 11

Keep water in urine (lose lots of urine)

Question 12

How does furosemide act as an diuretic

Answer 12

Blocks, sodium, chloride and potassium cotransporter in the thick ascending limb.

Question 13

When is furosemide used

Answer 13

In cardiac and renal failure (volume overload)

Question 14

What are the side effects of using furosemide

Answer 14

Naturesis (loss of sodium)
Diuresis (loss of water)
Hypokalemia (loss of potassium)

Question 15

Is the descending limb permeable or impermeable to water

Answer 15

Permeable

Question 16

Which mechanism allows the movement of water from the descending limb to the interstitial space

Answer 16

Countercurrent mechanism

Question 17

What is the countercurrent mechanism

Answer 17

1) As the thick ascending limb pumps sodium, chloride and potassium into the interstitial space, it creates a high osmolality in the space.
2) this creates a osmolality gradient in the space
3) water from the descending limb therefore flows into the medulla

Question 18

What is the next structure after the loop of henle

Answer 18

Distal tubule

Question 19

Where is the distal tubule situated

Answer 19

Cortex

Question 20

Which ions are absorbed in the distal tubule

Answer 20

Sodium

Chloride

Question 21

How are the ions absorbed in the distal tubule from the apical membrane through the basolateral membrane

Answer 21

Apical membrane

1) sodium/chloride cotransporter brings the ions into the cell

Basolateral membrane

2) sodium/potassium pump brings sodium out and potassium in
3) the potassium that has entered moves back out through the boas lateral membrane with chloride by the potassium/Chloride transporter.

Question 22

What inhibits the sodium/chloride transporter on the apical membrane

Answer 22

Thiazides

Question 23

What is thiazides therefore classed as

Answer 23

Diuretics

Question 24

What is the role of diuretics

Answer 24

Lose lots of volume of water in urine

Question 25

Which structure comes after the distal tubule

Answer 25

Collecting duct

Question 26

Which molecules are absorbed in the collecting duct

Answer 26

Water
Sodium
Urea

Question 27

Describe the process of reabsorption of sodium and water from the apical membrane through the basolateral membrane

Answer 27

Apical membrane:

1) water moves in through AQP2 channels
2) sodium moves in via sodium channels

Basolateral membrane

3) AQP3 allows water to move into the medullary interstitial space
4) sodium moves out by sodium potassium pump

Question 28

What happens to the potassium that is brought into the cell through the basolateral membrane

Answer 28

Moves out into the filtrate of the collecting duct via potassium channels on the apical membrane

Question 29

Which hormone increases the number of AQP2 on the apical membrane

Answer 29

ADH/vasopressin

Question 30

Which hormone from the adrenal cortex increases the synthesis of sodium channels

Answer 30

Aldosterone

Question 31

What is the role of amiloride

Answer 31

Inhibit sodium channels on the apical membrane

Question 32

What is the role of spironolactone

Answer 32

Blocks the action of aldosterone to synthesis sodium channels

Question 33

How is urea reabsorbed in the collecting duct

Answer 33

1) via UT-A1 channels
2) this also increases the osmolality in the interstitial space so more water is reabsorbed from the descending limb of the loop of henle

Question 34

Which channel reabsorbs urea

Answer 34

UTA1 in the collecting duct

Question 35

Which hormone increases the expression of UTA1

Answer 35

ADH

Question 36

Where are urea reabsorbed so that some of the urea in the medulla enter back the nephron

Answer 36

The collecting duct

Question 37

Which channel reabsorbs the urea

Answer 37

UTA2

Question 38

What does the secretion and reabsorption of urea known as

Answer 38

Urea countercurrent