Physiology - The Proximal Tubule

Question 1

how much fluid and salt are reabsorbed in the kidneys?

Answer 1

99%

Question 2

how much glucose and amino acids are reabsorbed in the kidneys?

Answer 2

100%

Question 3

how much urea is reabsorbed in the kidneys?

Answer 3

50%

Question 4

how much creatinine is reabsorbed in the kidneys?

Answer 4

0%

Question 5

what is the initial segment of the nephron?

Answer 5

the proximal tubule

Question 6

how much fluid/min is reabsorbed in the proximal tubule?

Answer 6

around 80ml/min

Question 7

what is the osmolarity of the fluid reabsorbed in the proximal tubule?

Answer 7

300 mosmol/l

iso-osmotic with the filtrate

Question 8

what five things are reabsorbed in the proximal tubule?

Answer 8

sugar 
amino acids 
phosphate 
sulphate 
lactate

Question 9

what is secreted in the proximal tubule? (6)

Answer 9

hydrogen 
hippurates
neurotransmitters 
bile pigments
uric acid 
drugs and toxins

Question 10

what are the two methods of reabsorption in the tubules?

Answer 10

transcellular

paracellular

Question 11

what is transcellular reabsorption?

Answer 11

reabsorption into the interstitial fluid by passing through the tubular epithelial cell

Question 12

what is paracellular reabsorption?

Answer 12

reabsorption into the interstitial fluid by passing through the tight junctions of the tubular cells

Question 13

what is primary active transport?

Answer 13

transport that requires energy to operate the carrier

substrate moved against its concentration gradient

Question 14

what is secondary active transport?

Answer 14

carrier molecule is transported coupled to the concentration gradient of an ion

usually sodium

Question 15

what is facilitated diffusion?

Answer 15

passive carrier mediated transport of a substance down its concentration gradient

Question 16

where in the nephron are sodium ions reabsorbed?

Answer 16

all regions except the descending limb of the loop of henle

Question 17

what drives net sodium ion reabsorption in the nephron?

Answer 17

the basolateral sodium potassium pump

Question 18

how does sodium exit the tubular epithelial cell?

Answer 18

sodium potassium pump

Question 19

how does sodium enter the tubular epithelial cell?

Answer 19

sodium dependent glucose transporter
sodium dependent AA transporter
sodium hydrogen counter transporters

Question 20

what is the net movement of sodium in the proximal tubule and what does this mean for water?

Answer 20

from filtrate to blood

water moves in this direction

Question 21

how is water reabsorbed in the proximal tubule?

Answer 21

via the paracellular route

Question 22

how does glucose enter the tubular epithelial cell?

Answer 22

via the sodium glucose transporter

Question 23

how does glucose leave the tubular epithelial cell?

Answer 23

via facilitated diffusion

Question 24

what is the net movement of glucose in the proximal tubule?

Answer 24

from tubular fluid to blood

Question 25

what is the transport maximum?

Answer 25

the max rate at which a substance can be reabsorbed

Question 26

what is the renal threshold?

Answer 26

the concentration at which reabsorption of a substance plateaus

Question 27

what is the renal threshold of glucose?

Answer 27

10-12 mmol/l