Brainscape's Knowledge GenomeTM

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


See full index

Year 2 Renal > Glomerular filtration > Flashcards

Glomerular filtration Flashcards

1
Q

What are the basic renal processes?

A

Filtration

Reabsorption

Secretion

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

What is filtration?

A

The formation of an essentially protein-free filtrate of plasma - which takes place at the glomerular capillaries

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

What is the Glomerular filtration rate?

What are its normal values?

A

GFR describes the amount of fluid (the filtrate of plasma) that flows through the kidneys each minute - ie how well the kidneys are working

125 mls/min

180 L/day

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

What is the purpose of reabsorption in the kidneys?

Where does it take place?

A

Substances that the body wants are reabsorbed, those it doesn’t want stay in the tubule and are excreted

Takes place in both the proximal and distal tubule

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

What is the purpose of the secretion process in the kidneys?

Where does it take place?

What is secreted?

A

Provides a way to remove specific substances from the body

Both Proximal and distal tubules

Proximal - organic ions, some drugs

Distal - K+ and H+

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

How much blood flows through the kidneys?

Does this predispose it to any pathologies?

A

1200 mls/min

This is 20-25% of our total cardiac output

Total blood volume passes through in about 5 mins

The fact that the kidneys normally receive such a high BF explains their vulnerability to damage by vascular disease

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

What components of the blood are not allowed to enter the kidneys?

A

None of the red cells and only a fraction of the plasma proteins are filtered through into Bowman’s capsule

All these components just pass through efferent arterioles into the peritubular capillaries and then into the renal vein

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

What is renal plasma flow?

How do you calculate it?

What is its normal value?

A

Plasma constitutes about 55% of our total BV

0.55 x 1200 ml/min = 660 ml/min = renal plasma flow

Renal plasma flow is just how much PLASMA the kidneys receive through the renal arteries

Normal value is 660 ml/min

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

What is meant by the filtration fraction?

Figure out its normal value

normal renal plasma flow = 660 ml/min

normal GFR = a number that you should know

A

Kidneys as a whole receive 660 ml of plasma each minute

GFR = 125 ml/min - so the glomerular stuff removes 125ml’s of the 660ml’s each minute

Filtration fraction so for some stupid fkn reason its a percentage

125/660 x 100 = 19%

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

What are the forces that drive plasma through the glomerular capillaries?

A

Glomerular Filtration occurs in exactly the same way as fluid filters out of any capillary in the body

It is a balance between hydrostatic forces (favouring filtration) and oncotic pressure forces (favouring reabsorption)

These are called the Starling forces

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

What features are present in the glomerular capillaries that affect its permeability?

A

Fenestrations (pores):

  • fenestrations of glomerular endothelial cells do not allow RBC’s through but allow all other components of the plasma through

Basal lamina:

  • Does not allow passage of larger proteins

Slit membranes between Pedicels:

  • Does not allow passage of medium-sized proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the differences in pressure between glomerular capillaries and other capillaries

Why is this?

A

PGC is higher than most of the capillaries of the body

Afferent arterioles are short and wide - so offer little resistance to flow

Efferent arterioles are long and thin - so there is high post-GC resistance

Creates a sort of traffic jam - creating really high pressure in the glomerular capillaries

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

In terms of the starling forces - describe the net flow in the glomerular capillaries

A

Glomerular capillaries ALWAYS have higher hydrostatic pressure than oncotic pressure

PGC >> πp

Only filtration occurs at the glomerular capillaries

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

Give an equation for the Net filtration pressure into Bowman’s capsule

What is the normal value in humans?

A

NFP = PH - π - Pfluid

10 mmHg

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

What factors affect GFR?

A

Subject to both extrinsic and intrinsic control

Extrinsically:

  • Sympathetic vasoconstriction
  • Catecholamines
  • Angiotensin II

Intrinsically:

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

Describe the extrinsic control of GFR

A

Sympathetic vasoconstriction:

  • Sympathetic nerve stim causes vasoconstriction in both
    • afferent arteriole has greater sensitivity

Circulating catecholamines:

  • Primarily causes afferent vasoconstriction

Angiotensin II:

  • constriction, of efferent at [low], both afferent and efferent at [high]
17
Q

Describe the effect of sympathetic stimulation on Glomerular Pressure and thus GFR

A

Sympathetic stimulation would reduce GFR

Fight or flight response reduces kidney filtration function to allow more blood to pump the muscles eh

18
Q

What is the effect of Angiotensin II on the GFR?

a) at high [Ang]
b) at low [Ang]

A

[Low] - efferent constriction = Increased GFR

[High] - afferent and efferent constriction = Decreased GFR

19
Q

Describe the intrinsic control of GFR (autoregulation)

What range of BP does it work over?

Describe the intrinsic response to increased BP

A

BF and GFR kept relatively constant due to autoregulation

Works within the range of 60-130 mmHg

If mean arterial pressure increases - there is an automatic constriction of afferent arterioles

This prevents a rise in PGC and thus prevents an unwanted rise in GFR

20
Q

How does intrinsic and extrinsic control of GFR work?

A

In situations where Blood volume or blood pressure are compromised (eg haemorrhage) - then extrinsic controls can OVERRIDE autoregulation

This provides blood for usage in other tissues which need it more urgently

21
Q

What is the reabsorptive role of the peritubular capillaries?

A

Since 180 l/day are filtered through the glomerulus into the renal tubule, but only 1-2 l/day are excreted as urine an enormous amount of fluid must be reabsorbed back into peritubular capillaries

They are very long and narrow - it offers resistance along its entire length, there is a large P drop so that hydrostatic pressure is very low

22
Q

In terms of the starling forces - explain why there is reabsorption in the peritubular capillaries

A

Ppc - Hydrostatic pressure in peritubular capillaries is low

πp - oncotic pressure high compared to normal (loss of plasma earlier means its way more concentrated)

πp >> Ppc

23
Q
A

Year 2 Renal (15 decks)

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