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Renal > Lec 2/3 Renal Physiology > Flashcards

Lec 2/3 Renal Physiology Flashcards

1
Q

What percent of body mass it total water?

A

total body water is 60%

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2
Q

What percent of total body water is extracellular vs intracellular?

A

1/3 extracellular [20% total body]

2/3 intracellular [40% total body]

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3
Q

What percent of total extracellular water is plasma volume vs interstitial?

A

1/4 plasma volume [5% total body weight]

3/4 interstitial [15% total body weight]

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4
Q

What is total body fluid in liters?

A

40 liters

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5
Q

What is the function of glomerulus?

A

bulk filtration of urine

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6
Q

What is the function of proximal tubule?

A

bulk reabsorption of whats filtered [reabsorbs 2/3 of filtered fluid]

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7
Q

What is the function of the loop of henle?

A

to reasborb eletrolytes without water –> creates longitudinal gradient to allow potential for concentrating urine or secreting dilute urine

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8
Q

What is function of distal tubule and collecting duct?

A

fine tune what we excrete and acidification of urine

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9
Q

What are the two types of nephrons?

A

cortical and juxtamedullary

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10
Q

What are properties of cortical nephrons?

A
  • glomerulus near surface of kidney
  • shorter loop of henle –> Na and H2O wasting [excrete more]
  • efferent: peritubular capillaries that stay in cortex
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11
Q

What parts of kidney structures are contained in cortex?

A
  • glomeruli

- the convoluted portions of loop of henle = proximal and distal convoluted tubules

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12
Q

What are the 4 parts of the loop of henle?

A
  • thick descending limb
  • thin descending limb
  • thin ascending limb
  • thick ascending limb
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13
Q

What is the function of glomerulus?

A

form primary urine which is filtrate from plasma; filters plasma

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14
Q

What are properties of juxtomedullary nephrons?

A
  • glomerulus in cortex near medulla junction
  • longer loop of henle –> allows for more concentration [Na and H20 conserving]
  • efferent: vasa recta that follows loop of henle
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15
Q

What is the function of peritubular capillaries?

A

associated with cortical nephrons; stays in cortex exclusively and puts Na and H2O reabsorbed in prox and distal tubules back into circulation

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16
Q

What is function of vasa recta?

A

associated with juxtomedullary nephrons; network of long looping capillaries that follow path of loops of henle; aids in creating longitudinal gradient

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17
Q

What are characteristics of the content of bowman’s space?

A

exactly like plasm except not proteins, cells, or large macromolecules

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18
Q

What is the main function of the efferent arteriole?

A

down stream resistor; backs up fluid into the capillary to drive filtration/fluid into bowman’s space

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19
Q

What is the difference in glomerular vs systemic capillaries?

A

glomerular capillaries are in parallel not in series –> lower resistance than in systemic so lower pressure drop [only 2-3 mmHg drop] –> mean there is a much higher filtration pressure across the glomerulus compared to systemic circulation so filtration occurs across the entire length [vs in systemic filtration in beginning and reabsorption at the end]

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20
Q

What two structures make up the juxtaglomerular apparatus?

A
  • juxtaglomerular cells [JG cells] that secrete renin
  • macula densa: in distal tubule; sensitive to NaCl conc in distal tubule and feedback to control renin secretion and resistance of afferent arteriole to maintain constant GFR
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21
Q

What are the 3 layers of glomerular filtration barrier?

A
  • fenestrated capillary endothelim [size]
  • fused basement membrane with heparan sulfate [neg charge barrier]
  • epithelial layer of podocyte foot processes [filtration slits]
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22
Q

Is pos, neutral, or neg charged protein more likely to be able to pass glomerular filtration barrier?

A

positive charge can more easily pass filtration barrier b/c it has an inherent negative charge

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23
Q

What is the equation for GFR in terms of starlings forces?

A

GFR = K([Pgc - Pbs] - [PIgc-PIbc])

Pgc = hydrostatic P in glomerular capillary 
Pbs = hydrostatic pressure in bowmans space
PIgc = oncotic pressure in glomerular capillary
PIbs = oncotic pressure in bowman space = normal 0
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24
Q

What is the equation for clearance of a substance?

A 
C = UxV/Px
Ux = urine conc X
V = urine flow rate
Px = plasma conc X
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25
Q

What does it mean if Cx < GFR?

A

net tubular reabsorption

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26
Q

What does it mean if Cx > GFR?

A

net tubular secretion

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27
Q

What does is mean if Cx = GFR?

A

no net secretion or absorption

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28
Q

Clearance of what substance[s] can be used to calculate GFR?

A

inulin

creatinine is approximate but slightly overestimates

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29
Q

What is difference in Kf systemic vs glomerular capillary?

A

glomerular = much higher Kf

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30
Q

Clearance of what substance equals effective renal plasma flow?

A

PAH

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31
Q

What is the equation for filtration fraction [FF]?

A 
FF = GFR / RPF
RPF = renal plasma flow
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32
Q

What happens to GFR if you constrict the afferent artery?

A

increased resistance –> more pressure dissipates by the time you reach glomerular capillary so less hydrostatic P –> lower GFR and less blood flow into capillary [lower renal blood flow]

in sum: lower RBF, lower GFR

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33
Q

What happens to GFR if you dilate the afferent artery?

A

decreased resistance –> higher hydrostatic P –> higher GFR and more blood flow into capillary [lower renal blood flow]

in sum: higher RBF, higher GFR

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34
Q

What happens to GFR if you constrict the efferent artery?

A
  • higher resistance to blood flow so pressure builds up –> rise in Pgc and increase in GFR
  • decrease RBF, increase GFR
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35
Q

What happens to GFR if you dilate the efferent artery?

A
  • low resistance to blood flow so lower pressure –> decrease in Pgc and decrease in GFR
  • increase RBF, decrease GFR
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36
Q

What are two non-vascular regulators of GFR?

A
  • contraction of mesangial cells causes decrease K/GFR [vs relaxation causes increases]
  • contraction of podocytes decreases K/GFR [vs relaxation increases]
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37
Q

How does kidney autoregulate constant GFR [despite changes in MAP]? [2 mech]

A
  • myogenic mechanism: vascular smooth muscle stretched –> increase in contractile force leads to vessel contracting down to smaller diameter
  • tuboglomerular feedback: macula densa of distal tubule has contact w/ afferent arterole; senses luminal fluid in distal tubule and causes afferent arteriole contraction/relaxation
38
Q

When does kidney autoregulation fail?

A

at MAP < 60 an’t maintain perfusion pressure –> thus hypotension can cause renal failure

39
Q

What is the equation for filtered load of a substance?

A

FLx = Px * GFR

FL = filtered load
P = plasma conc
40
Q

What is equation for urinary excretion of a substance?

A

UEx = Ux * V

UE = urinary excretion
U = urine conc
V = urine flow
41
Q

What is equation for fractional excretion of a substance?

A

FEx = UEx / FLx

FEx = fractional excretion
UEx = urinary excretion
FLx = filtered load
42
Q

What is normal GFR?

A

125 mL/min or 180L/day

43
Q

What happens to H2O in the proximal tubule?

A
  • isosmotic reabsorption of water mediated by leaky tight junctions
  • primarily Na-driven/dependent
  • paracellular and transcellular
44
Q

What happens to water in descending loop of henle?

A

water permeable; passive reabsorption due to medullary hypertonicity

45
Q

What happens to water in ascending loop of henle?

A

ascending loop of henle is water impermeable

46
Q

What happens to water in early distal convoluted tubule?

A

water impermeable

47
Q

What happens to water in late distal tubule and collecting tubule?

A

permeability depends on ADH level; ADH acts at V2 recepro and inserts aquaporin H2O channels on luminal side

48
Q

In what part of the loop of henle does Na/K reabsorption occur?

A

occurs in thick ascending loop via Na/K/2Cl cotransporter

49
Q

What is important about function of Na/K/2Cl cotransporter?

A

only unctions if it contains all 3 ions
conc of Na > > K so have apical transport of K back into lumen to recycle for continued function of the Na/K/2Cl cotransport [otherwise you would be limited by the amount of K]

50
Q

What happens to glucose in the proximal tubule?

A

100% of glucose gets reabsorbed in the proximal tubule

51
Q

What is the osmolarity of the fluid at end of the distal prox tubule?

A

same as serum = very leaky/permeably

52
Q

What happens to conc of lumen in thick ascending limb?

A

have solute transport but it is water impermeable so get hypotonic solution that is delivered to the distal tubule

53
Q

How is Na handled in early proximal tubule?

A
  • lumen potential -4 mV
  • Na linked co-transporter reabsorbs Na/glucose; Na/AA, etc
  • each Na absorbed with a bicarbonate
  • basolateral side of cell has Na/K ATPase [3 Na out of cell; 2 K in = electrogenic]

65-80% of Na reabsorbed in prox tubule

54
Q

How is Na handled in late proximal tubule?

A
  • Na reabsorbed transcellular and pericellularly
  • pericellular = Cl driven Na reabsorption
  • transcelluar = Na/H exchanger then Na/K ATPase on basolateral side
55
Q

How is Na handled in descending loop of Henle

A

s

56
Q

What happens to Na in ascending loop of Henle?

A

10-20% of Na actively reabsorbed in thick ascending limb via Na/K/2Cl transporter

57
Q

What happens to Na in early distal convoluted tubule?

A

5-10% of Na reabsorbed
actively reabsorbed via Na/Cl cotransporter on apical; Na/K ATPase on basolateral side

further dilutes the urine b/c water impermeable

58
Q

What happens to Na in late distal tubule and collecting duct?

A

3-5% of Na reabsorbed
under hormonal regulation
principle cells: reabsorb Na and secrete K

overall: reabsorption of Na in exchange for secreting K and H

59
Q

What happens to K in the proximal tubule?

A

2/3 of filtered K reabsorbed in proximal tubule via paracellular = solvent drag; flows with H2O

60
Q

What happens to K in the thick ascending loop?

A

actively reabsorb via Na/K/2Cl
leaks back into lumen to recycle for use in Na/K/2Cl transporter thus creating + potential in the lumen which causes indirect paracellular reabsorption of Mg and Ca

61
Q

What happens to K in the late distal tubule and collecting duct?

A

alpha-intercalated cells: secrete H and reabsorb K

principle cells: reabsorb Na and secrete K

62
Q

What happens to Cl in early proximal tubule?

A

s

63
Q

What happens to Cl in late proximal tubule?

A

s

64
Q

What happens to Cl in late proximal tubule?

A
  • pericellular diffuses out of lumen down concentration gradient
  • transcellular enters cell via Cl/anion exchanger and leaves via Cl/K co-transporter
65
Q

What happens to Cl in descending loop of henle?

A

s

66
Q

What happens to Cl in ascending loop of henle?

A

s

67
Q

What happens to Cl in early distal convoluted tubule?

A

ss

68
Q

What happens to Cl in collecting duct?

A

s

69
Q

What happens to bicarbonate in the proximal tubule?

A

can’t be reabsorbed as bicarbonate; need to convert via carbonic anhydrase to CO2 and H2O; then back to HCO3 once in the cell

70
Q

What happens to bicarbonate in the proximal tubule?

A

s

71
Q

What happens to bicarbonate in the thick ascending limb?

A

reabsorbed as CO2 via carbonic anhydrase reaction in lumen/cell

72
Q

What happens to extra H in lumen when there is not bicarb left to reabsorb with it?

A
  • excreted as titratable acid
  • excreted as NH4

if pH is low in lumen –> will inhibit H ATPase so as to prevent even lower luminal pH which might injure epithelium; instead secrete H and NH4 which does not contribute to the pH

73
Q

What happens to acid-base handling in the distal tubule and collecting duct?

A

alpha intercalated cell

  • K/H ATPase on apical membrane to secrete H and reabsorb K
  • regenerates bicarb from intracellular CO2/H2o [also reabsorbs a small amount from lumen]
74
Q

What is the function of principle cells in the distal tubule and collecting duct? regulation?

A

principle cells reabsorb Na and secrete K

regulated by aldosterone and ADH

75
Q

What is the function of alpha intercalated cells in distal tubule and collecting duct?

A

secrete H and reabsorb K

76
Q

What is the function of beta intercalated cells in distal tubule and collecting duct?

A

secrete bicarbonate

77
Q

What two hormones regulate proximal tubule Na reabsorption?

A
  • epinephrine

- angiotensin II

78
Q

What who hormones regulate distal tubule reabsorption?

A
  • ANP [decreases reasborption]

- aldosterone

79
Q

What is the target for aldosterone?

A

principle cell –> increases K secretion

80
Q

What is the driving force for counter current multiplier?

A

Na/K/2Cl cotransporter is driving force; higher activity of cotransporter and longer the loop = larger the longitudinal gradient

81
Q

What are the 3 roles of ADH?

A
  • inserts water pores into apical membrane of principle cells
  • increases activity of Na/K/2Cl co-transporter to increase longitudinal gradient to create driving force for H2O reabsorption
  • increases permeability of urea in inner-medullary collecting duct
82
Q

What stimulates ADH release?

A

hyper-osmolarity and hypervolemia

83
Q

How is HCO3 reabsorbed basolaterally from alpha intercalated cells?

A

Cl/HCO3 countertransport

84
Q

How is HCO3 reabsorbed basolaterally from prox tubule and thick ascending limb cells?

A

via 1Na/3HCO3 cotransporter

85
Q

How is H secreted apically from prox tubule and thick ascending limb cells?

A

Na/H exchanger

86
Q

How is H secreted apically in alpha intercalated cells?

A

H/K ATPase exchanger

87
Q

What happens to HCO3, pCO2 in metabolic acidosis?

A
  • low HCO3

- low pCO2

88
Q

What happens to HCO3, pCO2 in metabolic alkalosis?

A
  • high HCO3

- high pCO2

89
Q

What happens to HCO3, pCO2 in respiratory acidosis?

A
  • high pCO2

- high HCO3

90
Q

What happens to HCO3, pCO2, in respiratory alkalosis?

A
  • low pCO2

- low HCO3

Renal (26 decks)

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