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Physiology III Final Exam > Glomerular Capillaries/Filtration > Flashcards

Glomerular Capillaries/Filtration Flashcards

1
Q

How is the glomerular capillary membrane different from others in the body?

A

3 layers instead of 2 enabling higher filtering abilities than an average capillary membrane (several hundred times greater)

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2
Q

What are the three layers of the glomerular capillary membrane?

A

1 endothelium
2 basement membrane
3 epithelial cell layer (podocytes)

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3
Q

Why do some things filter through the glomerular capillary membrane and others do not?

A

Dependent on pore size

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4
Q

What is the name for the BIG pores found in the glomerular capillary membrane?

A

Fenestrae

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5
Q

What is the name for the SMALL pores found in the glomerular capillary membrane?

A

Slit pores

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6
Q

What forms slit pores in the glomerular capillary membrane?

A

Pedicels of podocytes

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7
Q

Which layer of the glomerular capillary membrane possesses thousands of fenestrae?

A

Endothelium

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8
Q

What is the purpose of the negatively charged endothelium of the glomerular capillary membrane?

A

Prevents passage of plasma proteins

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9
Q

What layer of the glomerular capillary membrane is a meshwork of proteoglycan fibrillae and collagen?

A

Basement membrane

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10
Q

What is the purpose of the basement membrane of the glomerular capillary membrane?

A

Allows for the flow of water and small solutes to pass

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11
Q

What is the purpose of the negative charge associated with the proteoglycans of the basement membrane in the glomerular capillary membrane?

A

Inhibits passage of proteins

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12
Q

Which cells line the outer surface of the glomerulus?

A

Podocytes

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13
Q

Which layer of the glomerular capillary membrane possesses podocytes and slit pores?

A

Epithelium

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14
Q

What is the purpose of the epithelium of the glomerular capillary membrane being negatively charged?

A

Protects against plasma protein leakage

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15
Q

What occurs when the negative charge of the glomerular capillary membrane is lost?

A

Albumin is filtered and will appear in the urine with a frothy appearance (proteinuria/albuminuria)

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16
Q

How does filtration in the glomerulus work?

A

Pressure differentials between the fluid in the glomerulus and the fluid in the Bowman’s capsule

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17
Q

What is the term for the volume of blood plasma delivered to the kidneys per unit of time (mL/min)?

A

Renal Plasma Flow (RPF)

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18
Q

What is the term for the proportion of the fluid reaching the kidneys which passes into the renal tubules?

A

Filtration Fraction (FF)

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19
Q

What is a typical Filtration Fraction?

A

About 20%

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20
Q

What is the equation for glomerular filtration rate (GFR)?

A

Renal Plasma Flow X Filtration Fraction (RPF X FF)

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21
Q

What is a typical RPF?

A

550 mL/min (resting state)

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22
Q

What happens to RPF in an active state?

A

Increases (660-700 mL/min)

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23
Q

With typical RPF and FF rates, what would a typical GFR be?

A

110 mL/min (550 mL/min as RPF X .2 as FF)

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24
Q

How many liters of plasma fluid is filtered daily by our kidneys?

A

About 160 liters (we have 5 liters of total blood, therefore it is filtered multiples times per day)

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25
Q

How can the body increase GFR?

A

Altering RPF or FF

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26
Q

How can the body alter RPF?

A

Increasing overall cardiac output

Dilation of afferent arterioles in kidney

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27
Q

How can the body alter FF?

A

Contraction of efferent arterioles, increasing glomerular pressure

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28
Q

What forces determine GFR?

A

Balance of hydrostatic and colloid osmotic forces across capillary membrane

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29
Q

In what kinds of people do we see a high glomerular hydrostatic pressure and a large filtration coefficient in the kidneys?

A

Normal functioning non-pathologic adults

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30
Q

What does a large filtration coefficient represent?

A

Large filtering surface area

High permeability of the glomerular capillary

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31
Q

What is a typical filtration coefficient?

A

12.5 mL/min/mmHg (sum of hydrostatic and colloid osmotic forces)

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32
Q

What is another way to calculate GFR using the filtration coefficient?

A

Filtration coefficient X net filtration pressure

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33
Q

What measurements are used to find the net filtration pressure?

A

Hydrostatic and colloid osmotic pressures of BOTH the glomerular capillaries and inside the Bowman’s capsule (4 pressures)

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34
Q

What is the formula for net filtration pressure?

A

Glomerular hydrostatic P - Bowman’s capsular P - Glomerular colloid osmotic P + Bowman’s colloid osmotic P

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35
Q

What is another term for colloid osmotic pressure?

A

Oncotic pressure

36
Q

Which forces favor filtration?

A

Glomerular hydrostatic P (60 mmHg)

Bowman’s capsule oncotic P (0 mmHg)

37
Q

Which forces inhibit filtration?

A

Bowman’s hydrostatic P (18 mmHg)

Glomerular oncotic P (32 mmHg)

38
Q

What is a typical measurement of net filtration pressure?

39
Q

What effects are seen if we decrease the amount of functional glomerular capillaries?

A

Decreased surface area for filtration resulting in a decreased filtration coefficient

40
Q

What happens if we increase the thickness of a capillary membrane?

A

Decreases permeability of the capillary membrane resulting in a decreased filtration coefficient

41
Q

What effect does a decreased filtration coefficient have on GFR?

A

Decreases, as well

42
Q

What kinds of things can decrease the amount of functional glomerular capillaries?

A

Age or disease

43
Q

What kinds of conditions can increase the thickness of the glomerular capillary membrane?

A

Diabetes mellitus or hypertension

44
Q

Renal blood flow makes up about what percentage of cardiac output?

45
Q

Which consumes oxygen faster: kidneys or brain?

A

Kidneys (2X)

46
Q

Which has more blood flow: kidneys or brain?

A

Kidneys (7X)

47
Q

How do kidneys consume more oxygen than the brain?

A

High rate of active sodium reabsorption in the renal tubules

48
Q

What is the purpose of the kidneys having more blood flow than the brain?

A

Supplies kidneys with nutrients and enables removal of wastes
Supplies kidneys with enough plasma for a high rate of glomerular filtration

49
Q

Which part of the kidney receives most of the renal blood flow: medulla or cortex?

A

Cortex (medulla around 1-2% only)

50
Q

What vessels supply the renal medulla since it doesn’t receives the majority of the renal blood flow?

A

Vasa recta that descend into the medulla with the loops of Henle of the juxtamedullary nephrons

51
Q

What effect does mild-moderate sympathetic regulation have on blood flow and GFR?

A

Little effect, if any

52
Q

What kind of sympathetic response decreases GFR?

A

STRONG sympathetic activation

53
Q

What are examples of situations that could induce a strong sympathetic activation thus decreasing GFR?

A

Severe acute situations like defense reaction, brain ischemia, severe hemorrhage (MC)

54
Q

What effect do epinephrine and norepinephrine have on the kidneys?

A

Constriction of afferent and efferent arterioles

Decreased GFR

55
Q

When is endothelin (autacoid) released?

A

By vascular endothelial cells of the kidney during damage

56
Q

What is the effect of endothelin on the kidneys?

A

Vasoconstriction to decrease blood loss

Decreased GFR

57
Q

In what kinds of disease states do we see vasoconstriction induced by endothelin?

A

Toxemia of pregnancy, acute renal failure, uremia

58
Q

Is angiotensin II a powerful renal vasodilator or vasoconstrictor?

A

Renal vasoconstrictor

59
Q

When is angiotensin II typically released as a vasoconstrictor?

A

Due to decreased arterial pressure or volume depletion

60
Q

Where do we receptors for angiotensin II?

A

All blood vessels of the kidneys

61
Q

Which set of arterioles are most sensitive to angiotensin II?

A

Efferent (therefore constrict)

62
Q

Why aren’t afferent arterioles reactive to angiotensin II?

A

Stay dilated due to the release of vasodilators

63
Q

What is the overall purpose of the vasoconstriction caused by angiotensin II?

A

To maintain GFR in certain conditions

Decrease flow through peritubular capillaries to increase reabsorption of sodium and water

64
Q

What substance maintains vasodilation of the kidneys?

A

Endothelial-derived nitric oxide

65
Q

What is the purpose of endothelial-derived nitric oxide?

A

Allows normal excretion of sodium and water

66
Q

What kind of condition can result in decreased nitric oxide production resulting in increased renal vasoconstriction and increased blood pressure?

A

Atherosclerosis and damage to endothelium

67
Q

What effects are seen by prostaglandins and bradykinin on the kidneys?

A

Vasodilation, increased renal blood flow, and increased GFR

68
Q

What is the purpose of prostaglandins and bradykinin as vasodilators?

A

Counteract the vasoconstriction of afferent arterioles

69
Q

What kind of drugs can cause big reductions in GFR?

A

Nonsteroidal anti-inflammatory drugs like aspirin after surgery

70
Q

How is GFR affected by norepinephrine/epinephrine?

71
Q

How is GFR affected by endothelin?

72
Q

How is GFR affected by angiotensin II?

A

Prevents a decrease in GFR

73
Q

How is GFR affected by endothelial-derived nitric oxide?

74
Q

How is GFR affected by prostaglandins and bradykinin?

75
Q

What is the term for the intrinsic mechanism that keeps the blood flow and GFR relatively constant?

A

Autoregulation

76
Q

How much change do we see in GFR even when arterial pressure ranges from 75 mmHg to 160 mmHg?

A

Only about 10% change

77
Q

What would happen if we didn’t have autoregulation of the kidneys?

A

Increased blood pressure would result in depletion of blood volume

78
Q

What is the feedback mechanism present that links sodium concentration with renal artery resistance?

A

Tubuloglomerular feedback

79
Q

What is the purpose of tubuloglomerular feedback?

A

Ensures a constant delivery of sodium chloride to the distal tubules

80
Q

Renal cells can sense a decrease of what ion concentration?

81
Q

What substance is released in response to a decrease in sodium concentration?

82
Q

What two signals are initiated following the renal cells sensing a decrease in sodium?

A

Decreased resistance to blood flow in afferent arterioles

Release of renin

83
Q

What is the relationship between renin and angiotensin II?

A

Renin increases the formation of angiotensin II from angiotensin II

84
Q

What are the effects seen when resistance to blood flow in the afferent arterioles is decreased due to decreased sodium concentration AND with renin release?

A

Increased glomerular hydrostatic pressure

Increased GFR

85
Q

Renin release leads to the constriction of which vessels: efferent or afferent?

86
Q

What is the myogenic mechanism?

A

Ability of the individual blood vessels in the body to resist stretching during increased arterial pressure

87
Q

What is the supposed purpose of the myogenic mechanism?

A

Protect kidneys from damage during an increase in pressure

Physiology III Final Exam (6 decks)

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