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DEN 7101S Human Structure and Function II > Exam 3 Britton Renal Physiology I > Flashcards

Exam 3 Britton Renal Physiology I Flashcards

1
Q

Functions of the kidney

What is excreted?

A
  • Metabolic waste products
  • Chemicals and other bioactive substances
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2
Q

Functions of the kidney

What is regulated?

A
  • H2O and electrolyte balance
  • Acid-base balance
  • Arterial blood pressure
  • Red blood cell production (erythropoietin)
  • Vitamin D production
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3
Q

____ is the functional unit of the kidney

A

Nephron

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4
Q

Each kidney contains ____ nephrons

A

~ 1 million

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5
Q

The kidneys are well ____. Compared to other organs, blood flow is ____

A

Vascularized; high

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6
Q

Kidneys receive ____ % of the cardiac output at rest

A

25% (5 L/min, 1.25 RBF L/min or 180 L/day)

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7
Q

____ is necessary to expose the blood to filtration

A

High blood flow

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8
Q

Blood enters each kidney via a ____. Then branches into ____, ____, ____

A

Renal artery; interlobar arteries, arcuate arteries, interlobular arteries

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9
Q

How many capillary networks does the nephron have?

A

2

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10
Q

What are the capillary networks of the nephron?

A
  • Glomerular capillaries
  • Peritubular capillaries (vasa recta)
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11
Q

Which arterioles deliver blood to the glomerular capillaries?

A

Afferent arterioles (1st set of arterioles)

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12
Q

Which arterioles deliver blood to the peritubular capillaries?

A

Efferent arterioles

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13
Q

____ are the resistance vessels. The greatest drop in pressure occurs where?

A

Arterioles; Afferent and efferent arterioles

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14
Q

What is renal blood flow determined by?

A

Renal artery blood pressure and resistance in arterioles

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15
Q

Blood arrives at the kidneys via the ____ artery at ____

A

Renal artery; MAP (100 mmHg)

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16
Q

True or false: pressure in the glomerular capillary is low

A

False - it is high and constant, which is needed for filtration

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17
Q

Across different sections of renal blood vessels, pressure drops off in _____

A

Peritubular capillaries

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18
Q

What are the steps of urine formation?

A
  1. Filtration
  2. Reabsorption
  3. Secretion
  4. Excretion
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19
Q

During ____, plasma is filtered from the blood

A

Filtration

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20
Q

What happens during reabsorption?

A

Water and solutes are reabsorbed from the glomerular filtrate into the peritubular capillaries

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21
Q

What happens during secretion?

A

Metabolic waste and other substances are secreted from peritubular capillary blood into the nephron tubular fluid

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22
Q

During ____, the remainder of fluid is excreted as urine

A

Excretion

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23
Q

During the formation of urine, ____ L of filtrate per day yet only ____ L urine is produced

A

180; 1.5

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24
Q

____% of substances are reabsorbed and returned to circulation. What would happen if reabsorption did not occur?

A

> 99%; Most of the constituents of ECF would be rapidly lost in the urine

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25
Q

The proximal tubule is a key site for ____

A

Reabsorption (some filtrate substances are also reabsorbed in distal segments of the nephron)

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26
Q

What does urinary excretion of a substance depend on?

A

Its filtration, reabsorption, and secretion

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27
Q

What is the equation for amount of solute excreted?

A

Amount filtered - amount reabsorbed + amount secreted = Amount of solute excreted

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28
Q

____ is the first step in the formation of urine

A

Glomerular filtration

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29
Q

Where does filtration occur?

A

Renal corpuscle

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30
Q

What does the renal corpuscle consist of?

A
  • Glomerular capillaries
  • Bowman’s capsule
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31
Q

During glomerular filtration, what is filtered?

A

Low molecular weight substances that are freely dissolved in plasma

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32
Q

List examples of substances that are filtered during glomerular filtration

A
  • Glucose
  • Electrolytes (ions)
  • Amino acids
  • Peptides
  • Waste products (creatinine, urea)
  • H2O
  • Drugs
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33
Q

What is NOT filtered during glomerular filtration?

A
  • Cells (RBC, WBC, platelets)
  • Proteins
  • Lipoproteins
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34
Q

During glomerular filtration, ____ selects what molecules are filtered from the blood

A

The specialized structure of the glomerular filtration membrane

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35
Q

What is a filter?

A

A sieve that excludes solutes and proteins by electrical charge and size

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36
Q

What are the components of the glomerular filtration barrier?

A
  • Glomerular capillary endothelial cells
  • Glomerular basement membrane
  • Filtration slit diaphragm
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37
Q

Describe the structure and function of glomerular capillary endothelial cells

A
  • Flattened and highly fenestrated, resembling a sieve
  • Allow ultrafiltration of the blood
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37
Q

____ carries a net negative charge that repels proteins. Why does this happen?

A

Glomerular basement membrane; Proteins also carry a negative charge

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38
Q

The filtration slit diaphragm contains specialized epithelial cells called:

A

Podocytes

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39
Q

Podocytes project “tentacle-like” foot processes that ensheath the ____

A

Glomerular capillaries

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40
Q

Podocyte foot processes ____, leaving ____ between them. The slits are bridged by a ____ that prevents proteins and large molecules from entering the ____

A

Inter-digitate; narrow slits; filtration slit diaphragm; Bowman space

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41
Q

Glomerular filtration depends on the balance of ____ that act across the glomerular filtration barrier

A

Starling forces

42
Q

What are the 4 Starling forces present during glomerular filtration?

A
  • 2 hydrostatic pressures (1 in capillary blood Pgc, 1 in interstitial fluid Pbs)
  • 2 osmotic/colloid pressures (1 in capillary blood Tgc, 1 in interstitial fluid Tbs)
43
Q

____ is the sum of the hydrostatic and osmotic pressures that drive fluid out of the blood capillary to form the glomerular filtrate

A

Net filtration pressure

44
Q

In the glomerulus, Starling forces always favor ____

A

Filtration (always a positive number)

45
Q

What is the formula for net filtration pressure?

A

(Pgc + Tbs) - (Pbs + Tgc)
Forces favoring filtration - opposing filtration

46
Q

What is Kf?

A

Glomerular ultrafiltration coefficient

47
Q

What is the formula for Kf?

A

Surface area x capillary wall condictivity/integrity

48
Q

Vasoconstriction of the afferent arteriole - how is GFR likely to change?

A
  • Hydrostatic pressure in glomerular capillaries (Pgc) will fall
  • GFR will decrease
49
Q

Vasoconstriction of the efferent arteriole - how is GFR likely to change?

A
  • Pgc will increase
  • GFR will increase
50
Q

A kidney stone obstructs the ureter - how is GFR likely to change?

A
  • Hydrostatic pressure in Bowman’s capsule (Pbs) will increase
  • GFR will decrease
51
Q

A decrease in plasma protein concentration due to protein malnutrition - how is GFR likely to change?

A
  • Colloid pressure in the glomerular capillaries will fall
  • GFR will increase
52
Q

In the glomerulus, Starling forces always favor ____

A

Filtration

53
Q

In peritubular capillaries, Starling forces favor ____

A

Reabsorption

54
Q

What is the formula for blood flow?

A

Q = delta pressure/resistance

55
Q

Pressure is provided by ____. Resistance is provided mainly by ____

A

Systemic blood pressure (MAP); arterioles

56
Q

Kidneys have an ____ mechanism to maintain constant renal blood flow despite variations in blood pressure

A

Autoregulation

57
Q

In response to MAP variations in the range of ____ mmHg, autoregulation prevents changes to ___ and thus ____

A

80-180 mmHg; RBF; GFR

58
Q

RBF is maintained by altering what?

A

The resistance of afferent and/or efferent arterioles

59
Q

True or false: afferent and efferent arteriole resistance cannot be altered independently from each other

A

False - they can

60
Q

Autoregulation is mediated by what 2 mechanisms?

A
  • Myogenic response
  • Tubulo-glomerular feedback
61
Q

The myogenic response is also known as:

A

the Bayliss effect

62
Q

What is the myogenic response?

A
  • Constriction or dilation of afferent/efferent arterioles
  • Intrinsic mechanism independent of neural mechanisms
63
Q

The myogenic response involves ___ control of arteriole resistance by ____

A

Local; Local vasoactive substances

Local control is exerted through the direct action of local metabolites on arteriolar resistance

64
Q

Vasoactive substances have the effect of _______ arterioles, thus increasing or decreasing ___ respectively through this vascular effect

A

Constricting or dilating; MAP

65
Q

Overall, the ____ of the arterioles stabilizes RBF and thus GFR

A

Myogenic response

66
Q

The tubulo-glomerular feedback is mediated by _____

A

Juxtaglomerular apparatus (JGA)

67
Q

What does the juxtaglomerular apparatus consist of?

A
  • Afferent and efferent arterioles
  • Macula densa cells
  • Distal tubule
  • Mesangial cells
68
Q

In tubulo-glomerular feedback, juxtaglomerular cells function as ____

A

Intra-renal baroreceptors

69
Q

In tubulo-glomerular feedback, juxtaglomerular cells produce ___ which leads to the production of ____

A

Renin; ANG II (a potent vasoconstrictor)

70
Q

In tubulo-glomerular feedback, what do macula densa cells monitor?

A
  • The flow rate of filtrate through the DCT
  • NaCl composition of filtrate
71
Q

In response to changes detected in the filtrate, macula densa cells release ____ which control arteriole resistance in a paracrine mechanism. Macula densa cells can also stimulate JG cells to release ____

A

ATP and adenosine; renin

72
Q

What are some properties of inulin?

A
  • Freely filtered
  • Not reabsorbed or secreted
73
Q

What substance is used to measure GFR?

A

Inulin

74
Q

What is PAH?

A

Para-aminohippurate

75
Q

What are some properties of PAH?

A
  • Freely filtered
  • Not reabsorbed
  • Fully secreted
76
Q

What substance is used to measure effective renal plasma flow?

A

PAH

77
Q

____ is the amount of plasma that is completely cleared of any given substance per unit time

A

Renal clearance

78
Q

Know the renal clearance equation

A

Review equations

79
Q

Glomerular filtration rate is a measure of:

A

How well your kidneys filter blood

80
Q

____ is the volume of filtrate formed by both kidneys per minute

A

GFR

81
Q

Inulin is a substance that is freely filtered at the ____ but is neither ___ or ____ along the remainder of the tubule. ____% of inulin that filters into the tubule is excreted

A

Glomerulus; reabsorbed or secreted; 100%

82
Q

____ is used to estimate GFR

A

Creatinine

83
Q

What is creatinine?

A

A metabolic breakdown product of skeletal muscle creatine

84
Q

Creatinine is ____ and not ___, but it is ____, causing what?

A

Freely filtered; Reabsorbed; Secreted; 10-20% overestimate of GFR

85
Q

True or false: Serum creatinine may be measured to monitor kidney function

A

True

86
Q

What is the normal GFR for males?

A

125 mL/min

87
Q

What is the normal GFR for females?

A

105 mL/min

88
Q

GFR declines with:

A
  • Age
  • Chronic kidney disease
89
Q

GFR <15 mL/min indicates:

A

Kidney failure

90
Q

In a clearance ratio, the clearance of any substance can be compared with the clearance of ____

A

Inulin

91
Q

Clearance ratio = 1.0 when:

A

X equals the clearance of inulin

92
Q

Clearance ratio > 1.0 when:

A

Substance x is filtered and secreted

93
Q

Clearance ratio < 1.0 when:

A
  • X is not filtered
  • X is filtered and subsequently reabsorbed
94
Q

Renal plasma flow (RPF) is measured from the clearance of ____

A

PAH

95
Q

What is the value of effective RPF?

A

~ 600 mL/min

96
Q

10% of the PAH that passes through the kidney escapes ____

A

Secretion

97
Q

PAH clearance underestimates RPF by ____

A

10%

98
Q

Know the formula for renal blood flow

A

RPF/1-hematocrit

99
Q

Formula for filtration fraction

A

GFR/RPF

100
Q

____ is the fraction of the RPF that is filtered across the glomerular capillaries

A

Filtration fraction

101
Q

Normal filtration fraction value

A

16-20%

102
Q

What is filtered load?

A

Amount of a substance filtered across the glomerular filtration membrane per unit time

103
Q

What is excretion rate?

A

Amount of a substance excreted in the urine per unit time

DEN 7101S Human Structure and Function II (21 decks)

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