Glomerular filtration Flashcards

1
Q

What are the 3 basic renal processes

A

filtration
reabsorption
secretion

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2
Q

Give some examples of substances reabsorbed

A

sodium chloride, water, glucose, amino acids

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3
Q

Give some examples of substances secreted

A

organic ions, drugs,

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4
Q

How much of the cardiac output do the kidneys receive and what is the significance of this?

A

20-25%

vulnerability to damage by vascular disease

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5
Q

What tissue in the body has the highest BF/g?

A

kidneys!

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6
Q

Why does the kidneys receive such a large blood flow?

A

filtration! - not for oxygen

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7
Q

How long does it take for the volume for the total BV to pass through the renal circulation?

A

5 mins

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8
Q

Are red cells filtered into bowmans capsule?

A

no

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9
Q

What is the renal plasma flow?

A

660mls/min

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10
Q

What is the % filtration fraction?

A

19% - usually say 20

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11
Q

What is glomerular filtration dependent on the balance between?

A

starling’s forces

hydrostatic and oncotic pressures

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12
Q

Which of hydrostatic and oncotic pressure favours reabsorption and which favours filtration?

A

Hydrostatic - filtration

oncotic - reabsorption

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13
Q

3 things the permeselectivity of glomerular barrier is dependent on

A

molecular size, charge and shape

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14
Q

How does the glomerulus make sure proteins don’t get filtered

A

fenestration pore - prevents filtration of blood cells only
basal lamina - prevents filtration of larger proteins
slit membrane between pedicles - prevents filtration of medium proteins

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15
Q

Is the glomerular capillary pressure higher or lower than most capillaries? why?

A

higher

afferent arteriole - short and wide and little resistance

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16
Q

Does the blood arriving at the glomerulus have high or low hydrostatic pressure?

A

high

17
Q

What is the efferent arteriole of the glomerulus like?

A

long and thin and high post capillary resistance

18
Q

If there is high resistance what happens to hydrostatic pressure upstream and downstream?

A

upstream increases

downstream decreased

19
Q

Why does only filtration occur at glomerular capillaries?

A

afferent and efferent arterioles contribute to high glomerular capillary hydrostatic pressure. This pressure always exceeds oncotic pressure and so only filtration occurs.

20
Q

primary factor affecting GFR

A

PGC - dependent on arteriolar diameter and resistance

21
Q

3 extrinsic controls affecting GFR

A

angiotensin 2
sympathetic VC nerves
catecholamines

22
Q

Is the afferent or efferent arteriole more sensitive to sympathetic VC control?

A

afferent

23
Q

How do circulating catecholamines affect the GFR?

A

constrict primarily the afferent arteriole

24
Q

What does angiotensin 2 do to the glomerular arterioles?

A

constrict efferent at [low] and both at [high]

25
Q

What is meant by autoregulation in terms of the renal vasculature?

A

intrinsic ability to adjust resistance in response to arterial bp changes
keep BF and GFR relatively constant

26
Q

What mbp is autoregulation effective over? when does it fall and when does it cease?

A

60-130mmHg
below 60
50

27
Q

What happens to the afferent arteriole if the MAP increases

A

increase in constriction and prevent a rise in glomerular PGC

28
Q

Is autoregulation dependent or independent of hormone and nerves?

A

independent

29
Q

In haemorrhage what can override autoregulation? why?

A

extrinsic controls eg sympathetic VC and A2

liberates blood for more immediately important organs

30
Q

How much blood can be directed elsewhere in expense of the kidneys?

A

800ml/min

31
Q

What happens in prep for a marathon to prevent taking away from kidney BF

A

adaption of skeletal muscle to become more efficient

32
Q

What volume of blood per day is
a - filtered at glomerulus
b - excreted

A

180l

1-2l

33
Q

Why does only reabsorption take place in the efferent arteriole?

A

oncotic pressure exceeds hydrostatic as 20% volume ahs been removed and is now more concentrated with proteins