Proximal Tubule and Loop of Henle

Question 1

What do the kidneys reabsorb?

Answer 1

99% fluid and salt
100% glucose and amino acids
50% urea
0% creatinine

Question 2

What amount of filtered fluid is reabsorbed in the proximal tubule?

Answer 2

80 ml/min

Question 3

What is iso-osmotic with filtrate?

Answer 3

fluid reabsorbed in the proximal tubule

Question 4

What is secreted in the proximal tubule?

Answer 4

H
Hippurates
NTs
Bile pigments
Uric acid
Drugs
Toxins

Question 5

What is reabsorbed in the pT?

Answer 5

sugars
amino acids
phosphate
sulphate
lactate

Question 6

What are the steps involved with tubular reabsorption?

Answer 6

transcellular

paracellular

Question 7

What are the types of carrier mediated transport?

Answer 7

primary active transport
secondary active transport
facilitated diffusion

Question 8

What diffuses through lipid bilayer?

Answer 8

O2 and CO2

Question 9

What diffuses through channels?

Answer 9

Na

Question 10

What is facilitative diffusion molecule?

Answer 10

glucose

Question 11

What is reabsorbed through primary active transport?

Answer 11

K and Na through Na-K ATPase - essential for Na reasborption

Question 12

What is reabsorbed through secondary active transport?

Answer 12

Na and Glucose

Question 13

What is the iso-osmotic fluid reabsorption across leaky PT due to?

Answer 13

standing osmotic gradient

oncotic pressure gradient

Question 14

How is glucose absorbed into the tubular epithelial cell?

Answer 14

SGLT

Question 15

How is water reabsorbed?

Answer 15

through the NaCl osmotic gradient

Question 16

What is the transport maximum for glucose?

Answer 16

2mmol/min

Question 17

What is the renal threshold for glucose?

Answer 17

10-12mmol/l

Question 18

What happens when Tm is reached?

Answer 18

clearance of reabsorbed or secreted substances is not constant

Question 19

What is Na reabsorption driven by?

Answer 19

Na-K ATPase

Question 20

What is the osmolarity of the tubular fluid?

Answer 20

300mosmol/l

Question 21

What is the function of the loop of henle?

Answer 21

generates a cortico-medullary solute concentration gradient

Question 22

WHat does the solute concentration gradient allow?

Answer 22

the formation of hypertonic urine

Question 23

How does the loop function?

Answer 23

as a countercurrent multiplier

Question 24

What is the function of the ascending limb?

Answer 24

Na and Cl reabsorbed in thick ascending limb

impermeable to water

Question 25

What is the function of the descending limb?

Answer 25

does not reabsorbed NaCl | highly permeable to water

Question 26

What ensures that NaCl is absorbed into the interstitial fluid?

Answer 26

K recycling

Question 27

What allows K recycling and Na, Cl reabsorption?

Answer 27

NKCC channel

Question 28

What blocks the NKCC channel?

Answer 28

loop diuretics

Question 29

What is the effect of solute being removed in the ascending limb?

Answer 29

tubular fluid is diluted and osmolality of interstitial fluid is raised

Question 30

How is the osmolality maintained?

Answer 30

interstitial solute cannot enter the descending limb

Question 31

What does the high osmolality allow?

Answer 31

water to leave descending limb by osmosis

Question 32

What type of fluid moves into the distal tubule?

Answer 32

200mOsmol/l

Question 33

What is the osmolarity at the renal pelvis?

Answer 33

1200mosmol/l

Question 34

What contributes to approx half of the medullary osmolality?

Answer 34

the urea cycle

Question 35

Where is urea impermeable?

Answer 35

the distal tubule

Question 36

Where is 50% of urea absorbed?

Answer 36

the collecting duct

Question 37

Where does urea diffuse passively?

Answer 37

into the loop of henle

Question 38

What is the purpose of countercurrent multiplication?

Answer 38

to concentrate the medullary interstitial fluid

Question 39

Why is counter current multiplication important?

Answer 39

to enable the kidney to produce urine of different volume and concentration according to the amounts of circulating ADH

Question 40

What is the Vu on normal fluid intake?

Answer 40

around 1ml/min

Question 41

what is the counter current exchanger?

Answer 41

the vasa recta run alongside the long loop of henle of the juxtamedullary nephrons

Question 42

Where does blood osmolality rise?

Answer 42

as it dips into the medulla - water loss and solute gained

Question 43

Where does blood osmolality fall?

Answer 43

as it rises back to the cortex - water gained and solute lost

Question 44

How does the countercurrent system solve the problem of NaCl being washed away by essential blood flow?

Answer 44

vasa recta capillaries follow hairpin loops vasa recta capillaries freely permeable to NaCl and water Blood flow to vasa recta is low

Question 45

What is the function of the countercurrent exchange?

Answer 45

ensures that solute is not washed away