Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ZA - Renal System > Glomerular Filtration > Flashcards

Glomerular Filtration Flashcards

1
Q

What are the 3 basic renal processes?

A

Filtration
Reabsorption
Secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Explain filtration.

A

Filtration occurs to form a protein free filtrate of plasma at the glomerular capillaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the level of the GFR per day?

A

180 l/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What kind of things are reabsorbed in the kidneys?

A

NaCl
Water
Amino acids
Sugars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why is secretion by the kidneys clinically important?

A

Important for drug secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why are kidneys so susceptible to damage by vascular disease?

A

It is a small organ that deals with very high volumes of blood at a time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Is all this high volume of blood filtered?

A

No, none of the big cells (RBC, WBC, platelets) are filtered in the bowman’s capsule

Only a small fraction of the plasma is actually filtered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens to the rest of the blood not filtered by the kidneys?

A

Passes via efferent arterioles into the peritubular capillaries and into the renal vein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How much blood is filtered by the kidney’s per min and how much is just plasma?

A

1200 mls/min

~55% - 660 mls/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the normal GFR per min?

A

125mls/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the filtration fraction?

A

GFR/Total renal plasma flow x 100

125/660 x 100 = 19%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is glomerular filtration dependant on?

A

Hydrostatic forces favouring filtration

Oncotic pressure forces (starlings) favouring reabsorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What affects the filterability of solutes across the glomerular filtration barrier?

A

Molecular size
Electrical charge
Shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What prevents filtration of blood cells but allows all components of blood plasma to pass through the glomerulus?

A

Fenestration of glomerular endothelial cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does the basal lamina of the glomerulus do?

A

Prevents filtration of larger proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What prevents filtration of medium sized proteins?

A

Slit membrane between pedicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is Pgc?

A

Glomerular capillary pressure

18
Q

Why is Pgc higher than most capillaries?

A

The afferent arteriole is short and wide and offers little resistance to flow meaning the blood arriving at the glomerulus still has a high hydrostatic pressure

Equally the efferent capillaries are long and narrow offering high post-capillary resistance

19
Q

What is the golden rule of circulation?

A

If you have a high resistance, hydrostatic pressure upstream is increased, while the pressure downstream is decreased

20
Q

Why is this high pressure needed in the glomerulus?

A

Hydrostatic pressure favours filtration while oncotic pressure favour reabsorption

So at the glomerular capillaries since the hydrostatic pressure is higher filtration will be favoured

21
Q

What is the pressure of the hydrostatic forces?

A

55 mmHg

22
Q

What is the opposing osmotic pressure and fluid pressure?

A

30 mmHG osmotic and 15mmHg fluid pressure

23
Q

So what is the net filtration pressure?

A

55 - (30+15) = 10 mmHG

24
Q

What is the 1y factor in normal physiology affecting GFR?

A

Glomerular capillary pressure which depends on the afferent and efferent arteriolar diameter’s and therefore resistance

25
Q

In what way are the glomerular capillaries subject to extrinsic control?

A

Sympathetic VC nerves = afferent and efferent vasoconstriction–> greater sensitivity of afferent arteriole
Circulating catecholamines - constriction of afferent
Angiotensin 2 - constriction of only efferent at low volumes and both at high volumes

26
Q

What happens to GFR in resistance is increased in afferent vessel? What happens when there is little resistance ?

A

Decreases as blood can’t get through

GFR increases with little resistance as more blood can get through which increases pressure

27
Q

What happens to GFR if resistance is increased in efferent vessel?

A

Increases even though less blood gets through as pressure is increased

28
Q

Renal vasculature has a BLANK ability to adjust its resistance in response to changes in BLANK

What does this help do?

A

Intrinsic
Arterial BP

Helps keep blood flow and GFR constant = autoregulation

29
Q

What range of mean BP is the autoregulation effective over?

A

60-130 mmHg

30
Q

What happens below 60 mmHg mean BP?

A

Filtration starts to fall

31
Q

What happens below 50 mmHg mean BP?

A

Filtration stops

32
Q

What happens if mean arterial pressure increases? Why does this happen?

A

Autonomic increase in afferent arteriolar constriction - if this did not happen glomerular capillary pressure would increase and so would filtration

33
Q

What happens if mean arterial pressure decreases?

A

Afferent vessel dilates to restore Pgc

34
Q

What is autoregulation independent of?

A

Nerves or hormones as it happens in denervated and isolated perfused kidneys

35
Q

Is there any interaction between intrinsic and extrinsic controls?

A

Yes - in situations when blood volume drops very low (haemorrhage)

The activation of sympathetic VC nerves and Angiotensin 2 overrides autoregulation (which would have sought to dilate afferent vessel to raise GFR) and instead constricts the vessels

This stops filtration allowing blood to be redirected to important organs

36
Q

What does prolonged reduction in renal blood filtration cause?

A

Irreparable damage which may then lead to death due to disruption of the kidney’s role in homeostasis.

37
Q

What % of blood plasma volume filters in the glomerulus/bowmans capsule?

A

20% the rest returns to systemic circulation

38
Q

What % of fluid is re-absorbed?

A

19%

39
Q

Peritubular capillaries are responsible for ?

A

Reabsorption

40
Q

How do we know reabsorption of fluid occurs?

A

Since 180 l/day are filtered through the glomerulus into the renal tubule, but only 1-2 l/day are excreted as urine

41
Q

Why is the efferent arteriole good for reabsorption

A

Because it offers resistance along its entire length, there is a large P drop so that hydrostatic pressure is very low - 15mmHg

So starlings forces are not opposed and actually increase and can cause reabsorption

42
Q

What causes Starling’s forces to increase in peritubular capillaries?

A

Since 20% of the plasma has been filtered. The blood remaining in the efferent arteriole and then the peritubular capillaries has a higher concentration of plasma proteins and therefore a higher con. of osmotic pressure

ZA - Renal System (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions