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HSF > HSF 4 - Unit 1 Physiology: Tubular Reabsorption and Secretion > Flashcards

HSF 4 - Unit 1 Physiology: Tubular Reabsorption and Secretion Flashcards

1
Q

water reabsorption %, filtration and excretion per day

A

99%; 180 L/day, 1.8 L/day

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2
Q

K+ reabsorption %, filtration and excretion per day

A

86.1%, 720 mEq/day, 100 mEq/day

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3
Q

Ca++ reabsorption %, filtration and excretion per day

A

98.2%, 540 mEq/day, 10 mEq/day

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4
Q

HCO3- reabsorption %, filtration and excretion per day

A

99.9+%, 4320 mEq/day, 2 mEq/day

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5
Q

Cl- reabsorption %, filtration and excretion per day

A

99.2%, 18,000 mEq/day, 150 mEq/day

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6
Q

Na+ reabsorption %, filtration and excretion per day

A

99.5%, 25,500 mEq/day, 150 mEq/day

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7
Q

Glucose reabsorption %, filtration and excretion per day

A

100%, 180 g/day, 0 g/day

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8
Q

Urea reabsorption %, filtration and excretion per day

A

44%, 54 g/day, 30 g/day

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9
Q

what is notable about K+ and Na+ absorption in the kidneys? why?

A

we lose more K+ than Na+, have to exchange K+ to reabsorb Na+ and then try to recapture the K+

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10
Q

what is notable about urea and water absorption in the kidneys? why?

A

reabsorption and secretion of urea helps us reabsorb or lose water respectively, necessary to maintain life

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11
Q

what is the filtered load? equation?

A

quantity of a particular solute that is filtered through the glomerulus into Bowman’s space per unit time; GFR * P[x]

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12
Q

what is the equation for excretion?

A

urine flow rate * urine [x]

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13
Q

how do we know if something has been reabsorbed or secreted? examples of each

A

Excretion is < Filtered Load = Reabsorption (Glucose & Na+)
Excretion is > Filtered Load = Secretion (PAH & Creatinine)

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14
Q

what are the 2 steps of reabsorption?

A

1) Passive or active movement of water and dissolved solutes from the fluid inside the tubule through the tubule wall (between or through renal epithelial cells) and into the interstitial fluid.
2) Water and these substances to move through the peritubular capillary walls back into your bloodstream, again, either by passive or active transport.

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15
Q

what forces create the ideal environment for reabsorption in the kidney? how was this environment created?

A

low hydrostatic (outward pressure) and elevated oncotic (protein sucking force) built from filtration

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16
Q

what does reabsorption of Na help with?

A

critical to water, Cl-, and urea reabsorption

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17
Q

what is the series of events of Na reabsorption helping reabsorption of other molecules?

A

reabsorption results directly in H2O reabsorption and increases the lumen’s negative potential; water reabsorption increases luminal chlorine concentration and urea concentration; urea leads to passive urea reabsorption, chlorine and lumen negative potential both leading to passive chlorine reabsorption

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18
Q

what limits the speed of reabsorption?

A

Tmax; determined by saturation of a limited number of transporters

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19
Q

what is Tmax? what does this mean for the kidney?

A

the point at which increases of a substance do not result in an increase in movement of a substance across a cell membrane, in the kidney this means that it will be secreted since it will not be reabsorbed

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20
Q

what is threshold?

A

the plasma [x] concentration at which [x] first appears in the urine

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21
Q

what ions get reabsorbed in the PT and what percentages of each?

A

Na+, Cl-, K+, H2O (67%)
HCO3- (80%)
glucose, AA’s, phosphate (98%)

22
Q

what gets secreted into the PT and what percent?

A

H+ (80%) and wastes like NH4+, drugs, toxins, bile salts, catecholamines via organic ion transporters

23
Q

what hormones work on the PT?

A

ANGII and phosphate via PTH, FGF23, Vitamin D (1alpha - hydroxylase)

24
Q

what is Fanconi’s syndrome?

A

generalized inhibition of the transporters in the PT, not allowing reabsorption of Na, Cl, HCO3, K, water, glucose, amino acids, and phosphate

25
Q

what is the significance of TF/P?

A

= tubular fluid / plasma concentration; if = 1 then means there was no reabsorption or secretion that has occurred in the PT, or reabsorption of water has occurred at the same rate as the substance in the PT; if <1 more substance reabsorbed than water in the PT; if >1 substance was not reabsorbed more than water and or the substance was secreted into the PT (ex: urea and creatinine)

26
Q

what is GTB?

A

= glomerulotubular balance; the ability of each successive segment of the PT to reabsorb a constant fraction of glomerular filtrate and solutes delivered to it, preventing large swings in urine volume and washout of the ECFV when GFR is high

27
Q

how does the nephron reabsorb the same relative amount of filtrate? how much is this?

A

67%; by reabsorbing more absolute amount of filtrate, happens because the higher GFR means a higher peritubular capillary oncotic pressure

28
Q

what is a normal GTB value? perfect? none?

A

normal: 125 GFR, 84 PT reabsorption, 124 for total reabsorption, 1 for urine volume, total reabsorption at 99.2%
perfect: 150 GFR, 101 PT, 149 total reabsorption, 1 urine volume, 99.3% total reabsorption
none: 150 GFR, 84 PT reabsorption, 124 total, 26 urine volume, 82.7% total reabsorption

29
Q

how do we get peritubular capillary fluid reabsorption?

A

lowering the capillary hydrostatic pressure and increase the capillary colloid osmotic/oncotic pressure, along with a higher filtration coefficient, Kf, which measures the membrane permeability to water (intrinsic property of capillary walls)

30
Q

what gets reabsorbed in the LOH? what percent?

A

water (not specific, only in thin descending)

Na, K, Cl, Ca (25%), HCO3- (10%) all happens in thick ascending

31
Q

what gets secreted in the LOH? what percent?

A

10% of H+, thick ascending

32
Q

what hormones work on the LOH?

A

ADH

33
Q

what is Barter’s syndrome?

A

inhibition of Na+ reabsorption at the LOH

34
Q

what is the luminal environment at the LOH? why is this significant?

A

positive lumen to drive calcium, also impermeable to water

35
Q

what is the mOsm of the LOH?

A

600-1200

36
Q

what is the mOsm of the DT?

A

100

37
Q

what gets reabsorbed at the DT?

A

Na, Cl, Ca (5%)

38
Q

what hormones work at the DT?

A

calcium via PTH and vitmain D

39
Q

what is Gitelman’s syndrome?

A

inhibition of Na at the DT

40
Q

what is special about the DT?

A

impermeable to water

41
Q

what types of cells are in the CCDs?

A

principal and intercalated

42
Q

principal cells reabsorption, hormones, and secretion

A

reabsorption: Na+ via ENaC, Cla
secretion: K+ via ROMK
hormones: ADH and Aldosterone

43
Q

intercalated cells reabsorption, hormones, and secretion

A 
type A -
reabsorption: K/HCO3
secretion: H+
type B - 
reabsorption: H+
secretion: K/HCO3
44
Q

reabsorption, hormones, and secretion of the MCD

A

reabsorption: Na, Cl, H2O, urea, HCO3
secretion: H
hormone: ADH

45
Q

what is the mOsm of the CCD?

A

100

46
Q

what is the mOsm of the MCD?

A

50-1200

47
Q

what is Liddle’s syndrome?

A

excitation of Na reabsorption in the principal cells of the DT and CD

48
Q

what is special about MCD?

A

water permeable

49
Q

what do creatinine and inulin concentrations look like throughout the nephron? why?

A

high throughout, lack of reabsorption, minimal/no active secretion, freely filterable

50
Q

what does the concentration of amino acids, glucose, bicarb look like throughout the nephron?

A

low, reabsorb them faster than water

51
Q

what is the concentration of salts in each part of the nephron and why?

A

PT = iso, peritubular oncotic pressure is high and 1 ratio because move at same rate as water
D-LOH = hyper, water leaves so more concentrated
A-LOH = hypo, pull out salts and impermeable to water
distal tubule = hypo, move out salts then some permeability to water
CT = adjusted, under hormonal control via aldosterone and ADH, ADH resorbs water to concentrate remaining salt

HSF (23 decks)

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