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Physiology > Renal 4 - Tubular Reabsorption and Secretion > Flashcards

Renal 4 - Tubular Reabsorption and Secretion Flashcards

1
Q

describe tubular reabsorption

A

-high capacity and variable
-very selective
- many electrolytes and nutrients almost completely reabsorbed
- most waste products poorly reabsorbed

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2
Q

describe tubular secretion

A

-variable
- important for certain electrolytes such as K+ and H+, drugs, toxins

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3
Q

what are the 2 different ways solute can be reabsorbed

A

-paracellular
-transcellular

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4
Q

how does fluid in the ISF enter the peritubular capillaries

A

bulk flow

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5
Q

what is the normal rate of peritubular capillary reabsorption

A

124 ml/min

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6
Q

what percentage of filtered sodium is reabsorbed

A

greater than 99%

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7
Q

what ways are sodium reabsorbed

A

transcellular and paracellular

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8
Q

describe transcellular sodium reabsorption

A

passive across apical membrane and active across basolateral membrane

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9
Q

what type of active transport might Na+ be on the apical membrane

A

secondary active and tied to the reabsorption of another substance

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10
Q

what is the TEPD

A

-transepithelial potential difference
- charge difference across epithelial cell
-negative charge in lumen

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11
Q

describe the secondary active transporters in the apical membrane and what are they

A

-Sodium glucose symporter
- sodium H+ antiporter
- both exhibit saturation, specificity, and competition

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12
Q

what molecules move through facilitated diffusion across the basolateral membrane

A

glucose, amino acids

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13
Q

what exhibits maximum rate that some substances can be transported across the epithelium

A

absorption or secretion

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14
Q

what is the renal threshold

A

the plasma concentration that saturates the carrier - tubular load

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15
Q

what happens when the transport maximum is reached for all nephrons

A

further increases in tubular load are not reabsorbed or excreted

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16
Q

what substances reach a transport maximum

A

glucose, amino acids, phosphate, sulfate, urate, creatinine, PAH

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17
Q

as [glucose]plasma increases what happens to [glucose]filtrate and glucose tubular load

A

[glucose]filtrate increases and glucose tubular load increases

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18
Q

what effect does Na+ reabsorption have on water

A

creates gradient for H2O reabsorption via osmosis

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19
Q

what area of the nephron is highly permeable to H2O

A

proximal tubule

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20
Q

what happens as H2O moves via osmosis

A

-carries other solvents along = solvent drage
- creates gradients for the passive reabsorption of other solute such as Cl- and urea

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21
Q

what area of the nephron is impermeable to water

A

ascending limb of loop of henle

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22
Q

what part of the nephron is water permeability regulated and what regulates it

A

collecting duct - ADH

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23
Q

Proximal tubule reabsorption of Na+, Cl-, urea and H2O exhibit _____

A

gradient-time transport

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24
Q

if water is reabsorbed to a greater extent than the solute, the solute will become ______ such as____

A

more concentrated in the tubule; creatinine and inulin

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25
if solute is reabsorbed to a greater extend than water, the solute will become _____ such as
less concentrated in the tubule; glucose, amino acids
26
what is the order of regional tubular transport
-early PCT and late PCT - loop of henle: thin descending limb, thin ascending limb, thick ascending limb -early distal tubule - late distal tubule and cortical collecting duct - medullary collecting duct
27
describe the cells in the proximal tubule
-high capacity for active and passive reabsorption - large number of mitochondria - large surface area on both apical and basolateral membranes - large number of membrane proteins - high permeability for H2O
28
what makes up the proximal tubule
proximal convoluted tubule and proximal straight tubule
29
what does the proximal tubule reabsorb
- 65% of filtered Na+, Cl-, HCO3- and K+ - all filtered glucose and amino acids
30
what does the proximal tubule secrete
- metabolic waste products such as H+, organic acids, and bases such as bile salts, oxalate, urate and catecholamines -drugs or toxins - PAH
31
what is the transport mechanism for Cl- reabsorption in the early proximal tubule
-paracellular -passive down electrochemical gradient - solvent drag
32
what is the transport mechanism for Cl- reabsorption in the late proximal tubule
- transcellular: apical secondary active via formate/Cl- antiporter and basolateral facilitated diffusion - paracellularly
33
what transporters for glucose are located on the apical and basolateral membrane for glucose in the early and late proximal tubule and what is their affinity and capcity
-SGLT2 on apical in early PT; low affinity, high capacity - GLUT2 on basolateral in early PT; low affinity, high capacity - SGLT1 on apical in late PT; high affinity, low capacity - GLUT1 on basolateral in late PT; high affinity, low capacity
34
what inhibitors are used in the treatment of type 2 DM
SGLT2 inhibitors
35
what percentage of glucose is absorbed in each the early PT and late PT
-90% in early PT -10% in late PT
36
how much Na+ and H2O are reabsorbed in PT
an isotonic solution
37
how much glucose, amino acids, and HCO3- are reabsorbed in the PT
- all glucose and amino acids - 65% HCO3-
38
what portion of the PT reabsorbs Cl- and urea
distal portion
39
describe creatinine reabsorption in the PT
not actively reabsorbed
40
what percentage of filtrate is reabsorbed by the end of proximal tubule
70% (126 L/day)
41
describe the permeability of the thin descending limb
- high H2O permeability via AQP-1: major role in concentration/dilution of urine -20% filtered load of water - no active solute transport - urea secretion via facilitated diffusion
42
describe the permeability of the thin ascending limb
- does not reabsorb significant amounts of any solutes - impermeable to water - urea secretion via facilitated diffusion
43
describe the permeability of the thick ascending limb
-impermeable to H2O and urea - major site of Na+, Cl-, K+ reabsorption (25% filtered load) and H+ secretion
44
by the end of the loop of henle, is more solute reabsorbed or water
more solute
45
what portion of the loop of henle forms part of the JGA
the distal end of the TAL
46
what transporter is characteristic of the TAL
Na+ 2Cl- and K+ secondary active co transporter
47
what percentage of filtrate is reabsorbed in the end of the loop of henle
20% 36 L/day
48
what does the early distal tubule do
-impermeable to H2O and urea - reabsorbs 5% of Na+ and Cl- -further dilutes filtrate
49
what is the early distal tubule known as
the diluting segment
50
what transporters are in the apical and basolateral membrane of the early distal tubule and what do they do
- Na+ Cl- co transporter in apical membrane moves Na+ and Cl- into cells from lumen - Na+ K+ ATPase transports Na into interstitium on basolateral membrane - Cl- diffused into ISF though Cl- channel in basolateral membrane
51
what are the 2 cell types in the late distal/cortical collecting duct
-principle cells - intercalated cells
52
what percentage do principal cells make up in the late distal/CCD
60-70%
53
what do principle cells do
-site of aldosterone and ADH action - reabsorb Na+ and H2O - secrete K+ - impermeable to urea
54
what identifies a principal cell
-Na+ K+ ATPase and K+ leak channel on apical membrane - Na+ leak channel and K+ leak channel on basolateral membrane
55
what do alpha intercalated cells do
-function important during acidosis - secrete H+ - reabsorb K+ and HCO3- - primary active transport of H+ across apical membrane can secrete H+ against a great concentration gradient
56
how do you identify alpha intercalated cells
-H+ ATPase and Cl- leak channel and H+ K+ ATPase on apical membrane - HCO3- Cl- antiporter and K+ leak channel on basolateral membrane
57
what is the function of beta intercalated cells
-function important during alkalosis - secrete K+ and HCO3- - REabsorb H+
58
how do you identify a beta intercalated cell
-HCO3- Cl- antiporter and K+ leak channel on apical membrane - H+ ATPase and H+ K+ ATPase and Cl- leak channel on basolateral membrane
59
what does the medullary collecting duct do
-processes less than 10% of Na+ and water but very important -site of aldosterone and ADH action - urea reabsorbed via facilitated diffusion - secretes H+ using same mechanism as alpha intercalated cells
60
what percentage of filtrate is reabsorbed at the end of the collecting duct
9% 16.5 L/day

Physiology (41 decks)

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