proximal convoluting tubule physiology Flashcards

1
Q

what is osmolality?

A

number of particles per Kg of solute (moles/Kg)

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2
Q

what is the osmolality in the proximal convoluted tubule?

A

300 mosm/L

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3
Q

what is tubular secretion?

A

substances moving from the blood into the kidney tubule (this is an active process)

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4
Q

what is tubular reabsorption?

A

-moving substances from the kidney tubule to the blood (Can be passive or active)

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5
Q

role of sodium potassium ATPase?

A
  • pumps 2 K+ into the cell

- pumps 3Na+ out of the cell

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6
Q

role of sodium glucose transporters?

A
  • Sodium is low in the cell (due to sodium potassium ATPase pumping out 3 sodium) so sodium can enter the cell with passive diffusion through the sodium glucose transporter
  • there are high levels of glucose in the cell so it cannot diffuse into the cell
  • however due to secondary active transport with the sodium glucose transporter, glucose can enter the cell through the sodium glucose transporter
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7
Q

what substances move into the cell with sodium through secondary active transport?

A
  • glucose (SGLT)
  • amino acids
  • lactate
  • H+ (sodium hydrogen antiporter, it moves out when sodium moves in)
  • H2O (water follows salt)
  • chloride
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8
Q

how does glucose enter the blood stream from the proximal convoluted tubule?

A
  • sodium potassium ATPase causes 3 Na+ ions to leave the cell, decreasing concentration of Na+ in the cell
  • Sodium then enters the cell through diffusion through the sodium glucose transporters, allowing glucose to also enter
  • glucose then passes through glucose transporters at the cell basolateral membrane and into the blood stream (capillaries)
  • lactate can also enter with glucose
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9
Q

how do amino acids enter the blood from the proximal convoluting tubule?

A
  • sodium-potassium ATPase pumps out 3Na+ from the cells causing a decrease of sodium concentration in the cell
  • sodium then moves from the proximal convoluted tubule and into the cell, allowing amino acids to also enter the cell, agaisnt their concentration gradient through secondary active transport
  • amino acids then leave the cell and enter the blood stream through their transporter
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10
Q

in normal physiological conditions how much glucose, lactate and amino acids are reabsorbed from the kidney tubules and into the blood?

A

100% of it

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11
Q

what allows H+ to enter the proximal convoluting tubule from the cell?

A

-the sodium hydrogen antiporter

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12
Q

how do Calcium, magnesium and potassium leave the proximal convoluting tubule and enter the blood stream?

A

-through paracellular transport (moving between the cells) and into the blood stream

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13
Q

what type of substance is urea?

A

lipid

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14
Q

how do lipids pass out of the proximal convoluting tubule?

A
  • lipid soluble substances can pass through the phospholipid bilayer
  • urea (lipid) can just pass straight from the proximal convoluting tubule, through the cell and into the blood stream
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15
Q

how much glucose is reabsorbed in the proximal convoluting tubule?

A

100%

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16
Q

how much salt and water is reabsorbed in the proximal convoluting tubule?

A

67%

17
Q

how does glucose pass out of the proximal convoluted tubule?

A

through facilitated diffusion

18
Q

how does O2 and CO2 get reabsorbed in the proximal convoluted tubule?

A

through diffusion through the lipid bilayer

19
Q

what affect does PTH have on the proximal convoluting tubule?

A

-it causes phosphate excretion from inside the cells into the proximal convoluting tubule

20
Q

what is plasma clearance?

A
  • the volume of plasma completely cleared of a particular substance per minute
  • each substance has its own specific plasma clearance value
21
Q

what can be used to clinically determine GFR and why?

A
  • inulin
  • as it is freely filtered and not absorbed, secreted or metabolised

therefore GFR= PC of inulin

22
Q

what is the plasma clearance of glucose and why?

A

plasma clearance of glucose= 0

-as glucose is filtered and then fully absorbed and not secreted

23
Q

what is the plasma clearance of urea and why?

A

-urea is filtered and partially reabsorbed, and not secreted

PC < GFR

24
Q

what is the plasma clearance of H+ and why?

A

H+ is filtered, secreted but not reabsorbed

the PC> GFR