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FA - Renal > Renal - Physiology (Basic Concepts) > Flashcards

Renal - Physiology (Basic Concepts) Flashcards

Pg. 525-527 in First Aid 2014 Pg. 480-482 in First Aid 2013 Sections include: -Fluid compartments -Glomerular filtration barrier -Renal clearance -Glomerular filtration rate (GFR) -Effective renal plasma flow -Filtration -Changes in glomerular dynamics -Calculation of reabsorption and secretion rate -Glucose clearance -Amino acid clearance

1
Q

What percentage of total body weight (kg) is total body water (L) versus nonwater mass?

A

60% total body water (L); 40% nonwater mass

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2
Q

Of total body water, what portion is extracellular versus intracellular fluid?

A

1/3 extracellular fluid; 2/3 intracellular fluid

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3
Q

What are the main extracellular fluid compartments? What portion of extracellular fluid is each?

A

Plasma volume - 1/4; Interstitial volume - 3/4

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4
Q

What is the major intracellular ion?

A

K+; Think: “HIKIN’ = HIgh K INtracellular”

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5
Q

What is the way to remember the % of body weight that applies to total body water, extracellular fluid, and intracellular fluid?

A

60-40-20 rule (% of body weight): 60% total body water, 40% ICF, 20% ECF

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6
Q

How is extracellular volume measured? How is plasma volume measured?

A

Extracellular volume measured by inulin; Plasma volume measured by radiolabeled albumin

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7
Q

What is the osmolarity (of plasma)?

A

290 mOsm/L

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8
Q

According to what 2 properties does the glomerular filtration barrier manage filtration?

A

Responsible for filtration of plasma according to size and net charge

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9
Q

What are the components of the glomerular filtration barrier? Where applicable, relate a component’s purpose to the overall function of the glomerular filtration barrier.

A

Composed of: (1) Fenestrated capillary endothelium (size barrier) (2) Fused basement membrane with heparan sulfate (negative charge barrier) (3) Epithelial layer consisting of podocyte foot processes

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10
Q

Which component of the glomerular filtration barrier acts to filter plasma according to size?

A

Fenestrated capillary endothelium (size barrier)

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11
Q

Which component of the glomerular filtration barrier acts to filter plasma according to charge?

A

Fused basement membrane with heparan sulfate (negative charge barrier)

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12
Q

What is lost in nephrotic syndrome? What are 4 associated consequences?

A

The charge barrier (of the glomerular filtration barrier) is lost in nephrotic syndrome, resulting in albuminuria, hypoproteinemia, generalized edema, and hyperlipidemia

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13
Q

What is renal clearance? Define it in both words and as a formula.

A

Cx = UxV/Px = volume of plasma from which the substance is completely cleared per unit time; (Note: Cx = clearance of X [mL/min], Ux = urine concentration of X (mg/mL), Px = plasma concentration of X, V = urine flow rate)

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14
Q

Give the fate of the substance x in the following scenarios: (1) Cx < GFR (2) Cx > GFR (3) Cx = GFR.

A

(1) Net tubular reabsorption of X (2) Net tubular secretion of X (3) No net secretion or reabsorption

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15
Q

What can be used to (accurately) calculate glomerular filtration rate (GFR), and why?

A

Inulin clearance can be used to calculate GFR because it is freely filtered and is neither reabsorbed nor secreted

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16
Q

What is the limitation of creatinine in terms of measuring GFR?

A

Creatinine clearance is an approximate measure of GFR. Slightly overestimates GFR because creatinine is moderately secreted by the renal tubules

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17
Q

What is a normal GFR?

A

100 mL/min

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18
Q

What is the clearance equation that equals GFR? What is another equation that can be used to define GFR?

A

GFR = U inulin x V/P inulin = C inulin; GFR = Kf [(Pgc - Pbs) - (PIgc - PIbs)] (Note: gc = glomerular capillary, bs = Bowman’s space, PI = mathematical pi, P = hydrostatic pressure, PI = oncotic pressure).

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19
Q

Again, what is the (Starling’s force) equation used to define GFR? Which component of this equation is normally zero?

A

GFR = Kf [(Pgc - Pbs) - (PIgc - PIbs)] (Note: gc = glomerular capillary, bs = Bowman’s space, PI = mathematical pi, P = hydrostatic pressure, PI = oncotic pressure); PIbs normally equals zero

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20
Q

What defines the stages of chronic kidney disease?

A

Incremental reductions in GFR define the stages of chronic kidney disease

21
Q

What can be used to estimate effective renal plasma flow, and why?

A

ERPF can be estimated using PAH clearance because it is both filtered and actively secreted in the proximal tubule. All PAH entering the kidney is excreted.

22
Q

What is the clearance equation that equals effective renal plasma flow?

A

ERPF = U pah x V/ P pah = C pah

23
Q

How does renal blood flow relate to renal plasma flow?

A

RBF = RPF/(1-Hct)

24
Q

How well does ERPF estimate true RPF?

A

ERPF underestimates true RPF by ~10%.

25
Q

What is the equation for filtration fraction (FF)? What is a normal FF?

A

FF = GRF/RPF; 20%

26
Q

What is the equation for filtered load?

A

Filtered load = GFR x plasma concentration

27
Q

With what can GFR be estimated?

A

GFR can be estimated with creatinine clearance

28
Q

With what is RPF best estimated?

A

RPF is best estimated with PAH clearance

29
Q

Create a visual labeling the following: (1) Proximal convoluted tubule (2) Parietal layer of glomerular capsule (3) Afferent arteriole (4) Juxtaglomerular cells (5) Efferent arteriole.

A

See p. 481 in First Aid for visual

30
Q

Which renal arteriole do prostaglandins affect? What are their effects on RPF, GFR, and FF? What blocks their effects?

A

Prostaglandins dilate afferent arteriole (increase RPF, increase GFR, so FF remains constant); NSAIDs

31
Q

Which renal arteriole does Angiotensin II preferentially affect? What are its effects on RPF, GFR, and FF? What blocks its effects?

A

Angiotensin II preferentially constricts efferent arteriole (decrease RPF, increased GFR, so FF increases); ACE inhibitor

32
Q

What do NSAIDs versus ACE inhibitors block?

A

NSAIDs block prostaglandins (which dilate afferent arteriole to increase RPF, decrease GFR, so FF remains constant); ACE inhibitors block Angiotensin II (which preferentially constricts efferent arteriole to decrease RPF, increase GFR, so FF increases)

33
Q

What is the effect of afferent arteriole constriction on: (1) RPF (2) GFR (3) FF (GFR/RPF)?

A

(1) Decrease (2) Decrease (3) NC

34
Q

What is the effect of efferent arteriole constriction on: (1) RPF (2) GFR (3) FF (GFR/RPF)?

A

(1) Decrease (2) Increase (3) Increase

35
Q

What is the effect of increased plasma protein concentration on: (1) RPF (2) GFR (3) FF (GFR/RPF)?

A

(1) NC (2) Decrease (3) Decrease

36
Q

What is the effect of decreased plasma protein concentration on: (1) RPF (2) GFR (3) FF (GFR/RPF)?

A

(1) NC (2) Increase (3) Increase

37
Q

What is the effect of constriction of ureter on: (1) RPF (2) GFR (3) FF (GFR/RPF)?

A

(1) NC (2) Decreased (3) Decreased

38
Q

Again, what is the equation for filtered load? What is the equation for excretion rate?

A

Filtered load = GFR x Px; Excretion rate = V x Ux

39
Q

How is reabsorption versus secretion calculated/defined?

A

Reabsorption = filtered - excreted; Secretion = excreted - filtered

40
Q

What is the fate of glucose at a normal plasma level (once filtered into the renal tubules)? What is the mechanism by which this occurs?

A

Glucose at a normal plasma level is completely reabsorbed in proximal tubule by Na+/glucose cotransport

41
Q

What is the plasma glucose level threshold at which glucosuria begins? What is the level at which all transporters are fully saturated (Tm)?

A

At plasma glucose of ~160 mg/dL, glucosuria begins (threshold); At 350 mg/dL, all transporters are fully saturated (Tm)

42
Q

For what condition is glucosuria an important clinical clue?

A

Diabetes mellitus

43
Q

What renal/urinary change does normal pregnancy cause, and why?

A

Normal pregnancy reduces reabsorption of glucose and amino acids in the proximal tubule, leading to glucosuria and aminoaciduria

44
Q

What happens to amino acids in the renal tubule, where, and via what mechanism?

A

Sodium-dependent transporters in the proximal tubule reabsorb amino acids

45
Q

What kind of disorder is Hartnup’s disease? What and where does it affect mechanistically?

A

Autosomal recessive disorder; Deficiency of neutral amino acid (e.g., tryptophan) transporters in proximal renal tubular cells and on enterocytes

46
Q

What percentage of total body weight are each of the following fluid compartments: (1) Total body water (2) Extracellular fluid (3) Intracellular fluid (4) Plasma volume (5) Interstitial volume.

A

(1) 60% (2) 20% (3) 40% (4) 5% (5) 15%

47
Q

What effects does Hartnup disease have?

A

Leads to neutral aminoaciduria and decreased absorption from gut –> results in pellagra-like symptoms

48
Q

How is Hartnup disease treated?

A

Treat with high-protein diet and nicotinic acid

FA - Renal (13 decks)

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