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Renal Exam 1 > Elements of Renal Function > Flashcards

Elements of Renal Function Flashcards

1
Q

Physiological functions of kidneys

-Eliminates?

A

-Eliminate metabolic wastes, foreign chemicals

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2
Q

Physiological functions of kidneys

-Produces what hormones?

A

-Erythropoietin, vitamin D, and renin

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3
Q

Physiological functions of kidneys

-Desgrades?

A

Peptide hormones

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4
Q

Physiological functions of kidneys

-Synthesis of?

A

Ammonia, prostaglandins, kinins, glucose

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5
Q

The kidneys are integrated with other body systems

-Ion balance?

A

Endocrine, gastrointestinal

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6
Q

The kidneys are integrated with other body systems

-Water balance?

A

CNS

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7
Q

The kidneys are integrated with other body systems

-Blood pressure, Na+, K+?

A

Autonomic NS, cardiovascular

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8
Q

The kidneys are integrated with other body systems

-Acid-base balance?

A

Respiratory, CNS

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9
Q

The kidneys are integrated with other body systems

-Elimination of wastes, toxins?

A

Liver

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10
Q

Understand the pictures and where fluid is going on slides 10 and 11

A

?

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11
Q

Types of nephrons

  • Cortical
    • Characteristics?
A
  • Short loops of Henle

- Surrounded by peritubular capillaries

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12
Q

Types of nephrons

  • Juxtamedullary
    • Characteristics?
    • Function?
A
  • Long loops of Henle
  • Long efferent arterioles are divided into specialized peritubular capillaries called the vasa recta
  • Function-concentrates urine
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13
Q

Renal Microcirculation

-Afferent arteriole–>?

A

Afferent arteriole–>glomerular capillaries–>efferent arteriole–>peritubular capillaries

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14
Q

Peritubular capillaries compared to vasa recta?

A
  • Peritubular capillaries run alongside loops of Henle of cortical nephrons
  • Vasa recta run alongside loops of Henle of juxtamedullary nephrons
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15
Q

Venous drainage

A

Interlobular vein–>arcuate v–>interlobar vein–>renal vein

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16
Q

Unusual aspects of renal microcirculation

  • Two sets of arterioles, two sets of capillary beds IN SERIES
    • First capillary network?
    • Second capillary network?
A

First capillary network-glomerular capillaries

Second capillary network-peritubular capillaries

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17
Q

Unusual aspects of renal microcirculation

  • Two sets of arterioles, two sets of capillary beds IN SERIES
    • First capillary network-glomerular capillaries
      - Hydrostatic pressure?
      - Amount of fluid filtered? Where does it go?
      - Oncotic pressure?
A
  • Hydrostatic pressure-high***
  • Large fluid volume filtered into Bowman’s capsule
  • Oncotic pressure-low
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18
Q

Unusual aspects of renal microcirculation

  • Two sets of arterioles, two sets of capillary beds IN SERIES
    • Second capillary network-peritubular capillaries
      - Hydrostatic pressure?
      - Amount of fluid filtered? Where does it go?
      - Oncotic pressure?
A
  • Hydrostatic pressure-low***
  • Large amounts of water and solute are reabsorbed
  • Oncotic pressure-high
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19
Q

Relative to cardiac output, how much blood do the kidneys receive at rest?

A

At rest the kidneys receive 20% of cardiac output

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20
Q

High pressure in the glomerular capillaries causes?

A

Filtration of blood

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21
Q

Lower pressure in the peritubular capillaries permits?

A

Fluid reabsorption

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22
Q

Pressure in both the glomerular and peritubular capillary beds can be regulated by?

A

resistance changes in afferent and efferent arterioles

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23
Q

What are the advantages of this high blood flow?

-Slide 16

A

?

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24
Q

Does renal fraction change during exercise?

A

Yes blood goes to muscles etc

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25
Q

Regional blood flow of kidney

-Higher blood flow in what part?

A

Higher blood flow in the cortex

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26
Q

Sympathetic innervation

-Sympathetic neurons synapse on?

A
  • Smooth muscle

- Granular cells

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27
Q

Sympathetic innervation

-Sympathetic neurons synapse on smooth muscle causing?

A

arteriolar constriction

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28
Q

Sympathetic innervation

  • Sympathetic neurons synapse on granular cells causing?
    • Through what type of receptor?
A

renin secretion

-Through beta adrenergic receptors

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29
Q

Effects of sympathetic stimulation?

-From Notes slide 19

A
  • Powerful constriction of afferent and efferent arterioles
  • Stimulates renin release from granular cells
  • Stimulates Na reabsorption in proximal tubule, thick ascending limb of Henle, DCT, CD
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30
Q

Effects of sympathetic stimulation

- Powerful constriction of afferent and efferent arterioles
     - Afferent compared to efferent?
     - Decreases?
     - Diverts?
A
  • Afferent > efferent
  • Decreases renal blood flow
  • Diverts the renal fraction to vital organs
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31
Q

Sympathetic discharge on the kidney results in (picture from book on slide 19)?

A
  • Decreased glomerular filtration rate
  • Increased reabsorption of Na and water from the PCT and DCT
  • Thirst (due to angiotensin II production)
32
Q

Effect of sympathetic discharge on renal regulation of body fluid and electrolytes
-The overall effect is fluid and electrolyte retention due to?

A
  • Decreased urinary output
  • Decreased urinary Na excretion
  • Increased water intake
33
Q

Basic processes of urine formation

-Glomerular formation?

A

-Filtration of plasma from glomerular capillaries into Bowman’s capsule

34
Q

Basic processes of urine formation

-Tubular reabsorption?

A

Transferral of substances from tubular lumen to peritubular capillaries

35
Q

Basic processes of urine formation

-Tubular secretion?

A

Transferral of substances from peritubular capillaries to tubular lumen

36
Q

Basic processes of urine formation

-Excretion?

A

Voiding of substances in the urine

37
Q

Quantitative relationships between the four basic processes

-Urinary excretion=?

A

Urinary excretion = amount filtered - amount reabsorbed + amount secreted

38
Q

Quantitative relationships between the four basic processes

-Tubular reabsorption?

A

-Tubular reabsorption = glomerular filtration - urinary excretion

39
Q

If excretion rate > filtration rate?

A

Tubular secretion must have occurred

40
Q

Physiologic importance of each process

  • For most substances, the rate of their filtration and reabsorption are large relative to their rate of excretion
    • Therefore?
A

Therefore, small changes in filtration or reabsorption can lead to large changes in excretion
-E.g. elevated plasma Na+ increases rate at which it is filtered and a smaller fraction of the filtered is reabsorbed, leading to an increased excretion

41
Q

Glomerular filtration rate (GFR)

  • Definition?
  • Normal percentage of total renal plasma flow?
A
  • Volume of plasma filtered into the combined nephrons of both kidneys per unit time (e.g. ml/min)
  • Normally around 20% of total renal plasma flow
42
Q 
Filtration rate (filtered load) of any FREELY FILTERED substance
   -Equation?
A

GFR x plasma concentration of substance

43
Q

Filtration rate example

  • If GFR=125 ml/min and plasma glucose conc.=2 mg/ml
    - What is filtration rate for glucose?
44
Q

Urinary excretion rate

-Equation?

A

Urine flow rate x concentration of substance in the urine

45
Q

Urinary excretion rate example

-If [Na] in urine is 20 mEq/l and urine excretion 2 l/day, what is the urinary excretion rate?

A

40 mEq/day

46
Q

Urinary excretion rate

-Reabsorption vs secretion?

A

Net rate of reabsorption or secretion of a substance=difference between glomerular filtration and urinary excretion (assuming substance is not produced or metabolized by the kidneys)

47
Q

If excretion is less than filtration?

A

net reabsorption occurred

48
Q

If excretion is greater than filtration?

A

net secretion occurred

49
Q

Example slide 26

50
Q

Renal Clearance

  • Definition?
  • Units?
A

The volume of plasma from which a substance is completely removed (‘cleared’) by the kidneys in a given time period
-Units are volume per time

51
Q

Renal clearance

-What does the clearance say about the kidneys?

A
  • Clearance describes how effectively the kidneys remove a substance from the bloodstream and excrete it in the urine
  • Different substances have different clearances
  • Measurement of GFR relies on the concept of clearance
52
Q

Calculation of clearance

-Equation-Clearance of substance A?

A

(Conc. of A in urine x urine volume)/conc. of A in plasma

Ca = (Ua x V)/Pa

53
Q

GFR can be estimated from clearance of certain compounds

-Requirements?

A

Compound must be freely filtered but CANNOT BE secreted, reabsorbed, produced, or degraded by the kidneys
GFR = (Ua x V)/Pa = Ca

54
Q

Inulin clearance = GFR

A

Inulin-freely filtered, neither reabsorbed, secreted, or metabolized

55
Q

Creatinine clearance approximates GFR

- Creatinine production?
- Normally?
A
  • Creatinine is produced endogenously from metabolism of creatine by skeletal muscle
  • Normally creatinine excretion = creatinine production
56
Q

Pcreatinine

-How is it used?

A

Pcreatinine is used for long-term monitoring of glomerular filtration and renal function

57
Q

Pcreatinine

-Relation to GFR?

A

Pcreatinine is inversely proportional to GFR

58
Q

As renal function (GFR) increases, what happens to creatinine clearance?

A

As renal function (GFR) increases, creatinine clearance will increase

59
Q

As GFR decreases, what happens to serum creatinine?

A

As GFR decreases, serum creatinine will increase

60
Q

BUN/creatinine ratio

  • If greater than 20/1, where is the problem relative to the kidney?
    • Mechanism?
A
  • Prerenal
  • Mechanism:
    • BUN reabsorption is increased
    • BUN is disproportionately elevated relative to creatinine in serum
    • Reduced renal perfusion due to hypovolemia
61
Q

BUN/Cr

- If 10-20/1, where is the problem relative to the kidney?
- Mechanism?
A
  • Normal range or postrenal (obstruction)
  • Mechanism:
    • BUN reabsorption is within normal limits
62
Q

BUN/Cr

- If less than 10/1, where is the problem relative to the kidney?
- Mechanism?
A
  • Intrarenal

- Renal damage causes reduced reabsorption of BUN and a low ratio

63
Q

BUN/Cr

-Principle behind this ratio?

A

Both BUN and Cr are freely filtered by the glomerulus, however BUN reabsorbed by the tubules can be regulated whereas creatinine reabsorption remains the same

64
Q

Another marker of GFR-Cystatin C

-Drawback of serum creatinine?

A

May vary according to muscle mass

65
Q

Cystatin C

A
  • Protein that is continuously produced by all cells
  • Freely filtered by the glomerulus
  • Similar to creatinine-serum levels rise if filtration is decreased but not dependent on muscle mass
66
Q

At low plasma concentration (below Tm?), how can you estimate renal plasma flow

A

Para-aminohippuric acid (PAH)

67
Q

Para-aminohippuric acid (PAH)

-Characteristics?

A
  • Freely filtered
  • Avidly secreted in the proximal tubule
  • Completely cleared from plasma of peritubular capillaries when plasma PAH conc. is low by secretion via OAT
68
Q

PAH and the Fick Principle

A

Amount of PAH which enters the kidney equals the amount leaving

69
Q

At low plasma concentration (below Tm) PAH clearance estimates?

A

Renal plasma flow

70
Q

Filtration fraction

  • what is it?
  • Equation?
A

Part of the renal plasma flow (RPF) that is filtered/diverted into the tubule
-FF = GFR/RPF

71
Q

Filtration fraction

-FF changes with?

A

Ultrafiltration pressure

72
Q

Filtration fraction

-With an increased FF what happens to the oncotic pressure of the efferent arteriole? What does this facilitate?

A

With an increased FF, the oncotic pressure of the efferent arteriole will increase, facilitating reabsorption of tubular fluid

73
Q

Normal FF?

A

around 20%

74
Q

Clinical application

-What would change the FF-Renal artery stenosis/severe hemorrhage?

A

In renal artery stenosis or severe hemorrhage renal blood flow (RPF) is reduced

  • A higher proportion of that flow reaching the kidneys must be passed into the renal tubules in order to maintain homeostasis
  • Reflected in a higher FF
75
Q

Physiological Functions of Kidneys

-Regulates what 4 things?

A
  • Regulate ECF solute concentration (osmolality)
  • Regulate plasma electrolyte concentrations
  • Regulate acid-base balance (H+ concentration)
  • Regulate ECF volume, arterial blood pressure

Renal Exam 1 (6 decks)

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