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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
How can the body increase GFR?
Altering RPF or FF
26
How can the body alter RPF?
Increasing overall cardiac output | Dilation of afferent arterioles in kidney
27
How can the body alter FF?
Contraction of efferent arterioles, increasing glomerular pressure
28
What forces determine GFR?
Balance of hydrostatic and colloid osmotic forces across capillary membrane
29
In what kinds of people do we see a high glomerular hydrostatic pressure and a large filtration coefficient in the kidneys?
Normal functioning non-pathologic adults
30
What does a large filtration coefficient represent?
Large filtering surface area | High permeability of the glomerular capillary
31
What is a typical filtration coefficient?
12.5 mL/min/mmHg (sum of hydrostatic and colloid osmotic forces)
32
What is another way to calculate GFR using the filtration coefficient?
Filtration coefficient X net filtration pressure
33
What measurements are used to find the net filtration pressure?
Hydrostatic and colloid osmotic pressures of BOTH the glomerular capillaries and inside the Bowman's capsule (4 pressures)
34
What is the formula for net filtration pressure?
Glomerular hydrostatic P - Bowman's capsular P - Glomerular colloid osmotic P + Bowman's colloid osmotic P
35
What is another term for colloid osmotic pressure?
Oncotic pressure
36
Which forces favor filtration?
Glomerular hydrostatic P (60 mmHg) | Bowman's capsule oncotic P (0 mmHg)
37
Which forces inhibit filtration?
Bowman's hydrostatic P (18 mmHg) | Glomerular oncotic P (32 mmHg)
38
What is a typical measurement of net filtration pressure?
10 mmHg
39
What effects are seen if we decrease the amount of functional glomerular capillaries?
Decreased surface area for filtration resulting in a decreased filtration coefficient
40
What happens if we increase the thickness of a capillary membrane?
Decreases permeability of the capillary membrane resulting in a decreased filtration coefficient
41
What effect does a decreased filtration coefficient have on GFR?
Decreases, as well
42
What kinds of things can decrease the amount of functional glomerular capillaries?
Age or disease
43
What kinds of conditions can increase the thickness of the glomerular capillary membrane?
Diabetes mellitus or hypertension
44
Renal blood flow makes up about what percentage of cardiac output?
22%
45
Which consumes oxygen faster: kidneys or brain?
Kidneys (2X)
46
Which has more blood flow: kidneys or brain?
Kidneys (7X)
47
How do kidneys consume more oxygen than the brain?
High rate of active sodium reabsorption in the renal tubules
48
What is the purpose of the kidneys having more blood flow than the brain?
Supplies kidneys with nutrients and enables removal of wastes Supplies kidneys with enough plasma for a high rate of glomerular filtration
49
Which part of the kidney receives most of the renal blood flow: medulla or cortex?
Cortex (medulla around 1-2% only)
50
What vessels supply the renal medulla since it doesn't receives the majority of the renal blood flow?
Vasa recta that descend into the medulla with the loops of Henle of the juxtamedullary nephrons
51
What effect does mild-moderate sympathetic regulation have on blood flow and GFR?
Little effect, if any
52
What kind of sympathetic response decreases GFR?
STRONG sympathetic activation
53
What are examples of situations that could induce a strong sympathetic activation thus decreasing GFR?
Severe acute situations like defense reaction, brain ischemia, severe hemorrhage (MC)
54
What effect do epinephrine and norepinephrine have on the kidneys?
Constriction of afferent and efferent arterioles | Decreased GFR
55
When is endothelin (autacoid) released?
By vascular endothelial cells of the kidney during damage
56
What is the effect of endothelin on the kidneys?
Vasoconstriction to decrease blood loss | Decreased GFR
57
In what kinds of disease states do we see vasoconstriction induced by endothelin?
Toxemia of pregnancy, acute renal failure, uremia
58
Is angiotensin II a powerful renal vasodilator or vasoconstrictor?
Renal vasoconstrictor
59
When is angiotensin II typically released as a vasoconstrictor?
Due to decreased arterial pressure or volume depletion
60
Where do we receptors for angiotensin II?
All blood vessels of the kidneys
61
Which set of arterioles are most sensitive to angiotensin II?
Efferent (therefore constrict)
62
Why aren't afferent arterioles reactive to angiotensin II?
Stay dilated due to the release of vasodilators
63
What is the overall purpose of the vasoconstriction caused by angiotensin II?
To maintain GFR in certain conditions | Decrease flow through peritubular capillaries to increase reabsorption of sodium and water
64
What substance maintains vasodilation of the kidneys?
Endothelial-derived nitric oxide
65
What is the purpose of endothelial-derived nitric oxide?
Allows normal excretion of sodium and water
66
What kind of condition can result in decreased nitric oxide production resulting in increased renal vasoconstriction and increased blood pressure?
Atherosclerosis and damage to endothelium
67
What effects are seen by prostaglandins and bradykinin on the kidneys?
Vasodilation, increased renal blood flow, and increased GFR
68
What is the purpose of prostaglandins and bradykinin as vasodilators?
Counteract the vasoconstriction of afferent arterioles
69
What kind of drugs can cause big reductions in GFR?
Nonsteroidal anti-inflammatory drugs like aspirin after surgery
70
How is GFR affected by norepinephrine/epinephrine?
Decreased
71
How is GFR affected by endothelin?
Decreased
72
How is GFR affected by angiotensin II?
Prevents a decrease in GFR
73
How is GFR affected by endothelial-derived nitric oxide?
Increased
74
How is GFR affected by prostaglandins and bradykinin?
Increased
75
What is the term for the intrinsic mechanism that keeps the blood flow and GFR relatively constant?
Autoregulation
76
How much change do we see in GFR even when arterial pressure ranges from 75 mmHg to 160 mmHg?
Only about 10% change
77
What would happen if we didn't have autoregulation of the kidneys?
Increased blood pressure would result in depletion of blood volume
78
What is the feedback mechanism present that links sodium concentration with renal artery resistance?
Tubuloglomerular feedback
79
What is the purpose of tubuloglomerular feedback?
Ensures a constant delivery of sodium chloride to the distal tubules
80
Renal cells can sense a decrease of what ion concentration?
Sodium
81
What substance is released in response to a decrease in sodium concentration?
Renin
82
What two signals are initiated following the renal cells sensing a decrease in sodium?
Decreased resistance to blood flow in afferent arterioles | Release of renin
83
What is the relationship between renin and angiotensin II?
Renin increases the formation of angiotensin II from angiotensin II
84
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?
Increased glomerular hydrostatic pressure | Increased GFR
85
Renin release leads to the constriction of which vessels: efferent or afferent?
Efferent
86
What is the myogenic mechanism?
Ability of the individual blood vessels in the body to resist stretching during increased arterial pressure
87
What is the supposed purpose of the myogenic mechanism?
Protect kidneys from damage during an increase in pressure

Physiology III Final Exam (6 decks)

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