Kidney Function 2

Question 1

Where is water reabsorbed in the nephron?

Answer 1

across the whole nephron but primarily in the proximal tubule

Question 2

What hormone regulates water reabsorption?

Answer 2

ADH

Question 3

Where is sodium reabsorbed in the nephron?

Answer 3

across the whole nephron but primarily in the proximal tubule

Question 4

What hormone regulates sodium reabsorption?

Answer 4

aldosterone

Question 5

Which ion is secreted in the nephron?

Answer 5

potassium

Question 6

What percentage of potassium is excreted?

Answer 6

10%

Question 7

What hormones regulate calcium retention?

Answer 7

parathyroid hormone and vitamin D3

Question 8

How is phosphate reabsorbed?

Answer 8

cotransport with sodium in the proximal tubule

Question 9

How is glucose reabsorbed?

Answer 9

cotransport with sodium in the proximal tubule

Question 10

What percentage of glucose is reabsorbed?

Answer 10

100%

Question 11

How are amino acids reabsorbed?

Answer 11

cotransported with sodium in the proximal tubule via 7 different transporters

Question 12

What percentage of creatinine is excreted?

Answer 12

100%

Question 13

What percentage of urea is excreted?

Answer 13

50%

Question 14

What is the concentration of the fluid in the cortex?

Answer 14

300mOsm - isotonic with plasma

Question 15

What is the concentration of filtrate at the base of the medulla?

Answer 15

1200mOsm

Question 16

What is the function of the proximal tubule?

Answer 16

Does the majority of reabsorption of water, sodium and other solutes

Question 17

What is the function of the descending limb of the loop of Henle?

Answer 17

It is impermeable to solutes but water permeable - so only water reabsorption will occur - water will be reabsorbed to equilibrate osmotically with the interstitial fluid

Question 18

What is the function of the ascending limb of the loop of Henle?

Answer 18

sodium reabsorption - at first passive reabsorption then active

Question 19

What is the osmolarity at the end of the loop of Henle?

Answer 19

100mOsm

Question 20

What is the variation in osmolarity at the end of the collecting duct?

Answer 20

50-1200mOsm

Question 21

Where do ADH and aldosterone act?

Answer 21

in the collecting duct

Question 22

What is the action of ADH?

Answer 22

inserts aquaporins into the collecting duct to increase water permeability so the water will be reabsorbed to equilibrate with the extracellular fluid

Question 23

What drives sodium reabsorption in the tubules?

Answer 23

Na+/K+ ATPase on the basolateral membrane

Question 24

What drives anion reabsorption in the tubules?

Answer 24

follows the electrochemical gradient

Question 25

How do anions move?

Answer 25

trancellularly and paracellularly

Question 26

What drives water reabsorption in the tubules?

Answer 26

moves by osmosis - follows solutes

Question 27

How does water move?

Answer 27

transcellularly and paracellularly

Question 28

What drives reabsorption of K+, Ca2+ and urea?

Answer 28

solvent drag - paracellular

Question 29

How is sodium reabsorbed in the proximal tubule?

Answer 29

sodium goes across the apical membrane passively via cotransporters and exchangers (with H+) and then goes across the basolateral membrane via the Na+/K+ ATPase - however there is also some paracellular movement particularly in the late proximal tubule

Question 30

How is HCO3- reabsorbed in the proximal tubule?

Answer 30

the Na+/H+ exchanger leads to HCO3- being reabsorbed

Question 31

How is Cl- reabsorbed in the proximal tubule?

Answer 31

both transcellularly and paracellularly - paracellular is dominant at first and then becomes transcellular

Question 32

How is sodium reabsorbed in the thin ascending limb of the loop of Henle?

Answer 32

paracellularly - due to concentration gradient

Question 33

How is sodium reabsorbed in the thick ascending limb of the loop of Henle?

Answer 33

Both transcellular and paracellular. Transcellular involves the Na+/K+/2Cl- cotransporter and also a Na+/H+ exchanger - it is then moved across the basolateral surface via the Na+/K+ ATPase

Question 34

What is the action of frusemide?

Answer 34

inhibits sodium potassium chloride cotransporter in the loop of henle (loop diuretic)

Question 35

Why is water not reabsorbed with the solutes in the thick ascending limb?

Answer 35

because the cell junctions are water tight

Question 36

How is Na+ reabsorbed in the distal tubule?

Answer 36

Entirely transcellular - apical via a Na/Cl cotransporter and basolateral via Na+/K+ ATPase. There is no paracellular route.

Question 37

What is the action of thiazide diuretics?

Answer 37

Block the Na/Cl cotransporter in the distal tubule

Question 38

How is sodium reabsorbed in the collecting duct?

Answer 38

At the apical membrane it is transported by sodium channels while there is potassium secretion in the opposite direction by potassium channels. At the basolateral membrane there is Na+/K+ ATPase

Question 39

How are endogenous organic acids absorbed?

Answer 39

Na dependent cotransporters on the apical membrane and H+ dependent cotransporters or organic anion exchangers on the basolateral membrane

Question 40

How are exogenous organic acids excreted?

Answer 40

organic anion exchanger

Question 41

What is the countercurrent mechanism?

Answer 41

The way that a gradient of increasing osmolarity is produced along the medullary pyramids. The loops of Henle are countercurrent multipliers and the vasa recta are countercurrent exchangers. Need the gradient in order to be able to concentrate urine. It is inhibited by loop diuretics.

Question 42

How do you make concentrated urine?

Answer 42

With ADH - add aquaporins to the membrane in the collecting duct so water comes out - however you need the concentration gradient