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Physiology #5 > RP4: Tubular Reabsorption and Secretion > Flashcards

RP4: Tubular Reabsorption and Secretion Flashcards

1
Q
A

early distal tubule cell

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2
Q
A

alpha intercalated cell

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3
Q
A

early proximal tubule cell

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4
Q
A

Beta intercalated cell

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5
Q
A

principal cell

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6
Q
A

thick ascending limb cell

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7
Q
A

late proximal tubule

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8
Q

How can solutes go from the lumen into the tubular cells?

A

paracellular path
transcellular path

using active or passive (diffusion)

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9
Q

How can water go from the lumen into the tubular cells?

A

osmosis paracellularly or transcellularly

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10
Q

How do solutes and water go from the interstitial fluid (basolateral side) to the peritubular capillaries?

A

bulk flow

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11
Q

When something travels from the tubular cell to the capillary via interstial fluid what is the process called?

A

reabsorption

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12
Q

Which membrane of the tubular cell is apical?

A

facing the lumen

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13
Q

Which membrane of the tubular cell is basolateral?

A

facing the peritubular capillary

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14
Q

Once fluid is reabsorbed across the tubule epithelium into the interstitial fluid, it enters peritubular capillaries via…

A

Bulk Flow

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15
Q

The normal rate of Peritubular Capillary Reabsorption is…

A

124 ml/min

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16
Q

Does sodium reabsorption occur Transcellular or Paracellular?

A

BOTH

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17
Q

Sodium reabsorption is passive or active across the apical membrane?

A

passive

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18
Q

Sodium reabsorption is passive or active across the basolateral membrane?

A

active

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19
Q

Why is sodium reabsorption passive across the apical membrane?

A

the transepithelial potential difference (TEPD) between the tubular lumen and interstitial fluid is -3 mV

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20
Q

What is transport maximum?

A

Maximum rate some substances can be transported across the epithelium (absorption or secretion)

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21
Q

What is renal threshold?

A

plasma concentration that saturates the carrier (tubular load)

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22
Q

Reabsorption of water is strickly…

A

passive (where ever the solutes go the water will follow)

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23
Q

__________ highly permeable to H2O

A

Proximal tubule

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24
Q

PT Reabsorption of Na+, Cl-, Urea and H2O exhibit…

A

Gradient-Time Transport

25
Q

Ascending limb of Loop of
Henle is permeable or not to water?

A

not permeable to H2O

26
Q

If water is reabsorbed to a greater extent than the solute, the solute will become _____ concentrated in the tubule

A

more

ex: creatinine, inulin

27
Q

If solute is reabsorbed to a greater extent than water, the solute will become ____ concentrated in the tubule

A

less

ex: amino acids, glucose

28
Q

What is unique about the cells of the proximal tubule?

A
  • high capacity for active/passive reabsorption
  • large # of mitochondria
  • large surface area
  • high permeability to H2O
29
Q

What does the proximal tubule reabsorb?

A

65% of…
Na+
Cl-
HCO3-
K+

all glucose
all amino acids

30
Q

What does the proximal tubule secrete?

A

metabolic waste products like H+, bile salts, toxins, drugs, and PAH

31
Q

What type of transport does the early proximal tubule use for Cl-?

A

paracellulary

32
Q

What type of transport does the late proximal tubule use for Cl-?

A
  • transcellular (apical - secondary active antiporter; basolateral - facilitated diffusion)
  • paracellular
33
Q

What type of transporters are in the early proximal tubule?

A

SGLT2
GLUT2

34
Q

What type of transporters are in the late proximal tubule?

A

SGLT1
GLUT1

35
Q

What type of transporters in the proximal tubule are in the apical membrane?

A

SGLT2 (early PT)
SGLT1 (late PT)

  • secondary active
36
Q

What type of transporters in the proximal tubule are in the basolateral membrane?

A

GLUT2 (early PT)
GLUT1 (late PT)

  • facilitated diffusion
37
Q

Where is 90% of the glucose reabsorbed?

A

early proximal tubule

38
Q

Where is 10% of the glucose reabsorbed?

A

late proximal tubule

39
Q

What is the affinity and capacity of the early proximal tubule transports (SGLT2 and GLUT2)?

A

low affinity
high capacity

40
Q

What is the affinity and capacity of the late proximal tubule transports (SGLT1 and GLUT1)?

A

high affinity
low capacity

41
Q

What transport inhibitor is used as a treatmetn for type 2 diabetes?

A

SGLT2 inhibitors (glifozins and invokana)

42
Q

How does the tubular fluid conc of Na+ and H2O change as it goes through the proximal tubule?

A

does not change (isotonic)

43
Q

How does the tubular fluid conc of glucose, amino acids, and HCO3- change as it goes through the proximal tubule?

A

decreases (reabsorbed into plasma)

44
Q

How does the tubular fluid conc of Cl-, urea, and creatinine change as it goes through the proximal tubule?

A

increases

45
Q

What percent of the filtrate is reabsorbed at the end of the proximal tubule?

A

70%

46
Q

What are the features of the thin descending limb of the loop of henle?

A
  • high H2O permeability
  • NO active solute transport
  • urea secretion via facilitated diffusion
47
Q

What are the features of the thin ascending limb of the loop of henle?

A
  • does not reabsorb anythign really
  • impermeable to water
  • urea secretion via facilitated diffusion
48
Q

What are the features of the thick ascending limb of the loop of henle?

A
  • impermeable to water and urea
  • major site of Na+, K+, Cl- reabsorption
  • H+ secretion
  • forms a hyposmotic solution
  • distal end forms the JG apparatus
49
Q

By the end of the loop of henle what type of solution is formed?

A

hyposmotic

50
Q

Where is the major site of Na+, K+, and Cl- reabsorption at?

A

thick ascending limb

51
Q

Since the thick ascending limb is impermeable to H2O what happens to the luminal osmolarity when solutes are reabsorbed?

A

osmolarity decreases

52
Q

What percent of the filtrate is reabsorbed by the end of the loop of henle?

A

20%

53
Q

What is the main functions of the early distal tubule?

A
  • absorbs solute without water
  • impermeable to water and urea
  • reabsorbs Na and Cl
  • further dilutes the filtrate
54
Q

What are the two cell types in the late distal/cortical collecting duct?

A
  • principal cells
  • intercalated cells
55
Q

What is the function of the principal cells in the late distal/cortical collecting duct?

A
  • aldosterone and ADH action
  • reabsorb Na+ and water
  • secrete K+
  • impermeable to urea
56
Q

What is the function of the alpha intercalated cells in the late distal/cortical collecting duct?

A
  • important in acidosis
  • secrete H+
  • reabsorb K+ and HCO3-
  • primary active transport of H+ across apical membrane
57
Q

What is the function of the beta intercalated cells in the late distal/cortical collecting duct?

A
  • important in alkalosis
  • secrete K+ and HCO3-
  • reabsorb H+
58
Q

What is the function of hte medullary collecting duct?

A
  • processes a small amount of Na+ and water (but important for regulation)
  • aldosterone and ADH action
  • urea reabsorbed via faciliated diffusion
  • secretes H+
59
Q

What percent of the filtrate is reabsorbed by the end of the collecting duct (final urine)?

A

9%

Physiology #5 (9 decks)

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