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Year 2- Urinary > Filtration > Flashcards

Filtration Flashcards

1
Q

What do the kidneys filter?

A

Blood

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2
Q

What is the main function of the kidneys?

A

To maintain homeostasis of the body

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3
Q

Where does filtration occur within the kidneys?

A

Glomerular capillaries

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4
Q

What is the purpose of filtration?

A

To form an essentially protein-free filtrate of plasma

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5
Q

How much is the Glomerular Filtration Rate (GFR)?

A

180L/day

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6
Q

What % of the cardiac output do the kidneys receive?

A

20-25%

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7
Q

How long does it take for total blood volume to pass through the kidneys?

A

Approx. five minutes

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8
Q

Important to note that none of the RBC’s or WBC’s and only a fraction of the plasma are filtered into the Bowman’s capsule.
Where does the rest of the plasma pass?

A

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

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9
Q

What is glomerular filtration dependant on the balance of?

A

The balance between hydrostatic forces favouring filtration and oncotic pressure forces favouring reabsorption

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10
Q

RECAP- what % of total blood volume does plasma make up?

A

55%

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11
Q

The glomerular barrier is selectively permeable. What factors determine if a substance can cross?

A

Molecular size
Electrical charge
Shape

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12
Q

List some substances which are freely filtered by the glomerular barrier.

A

Sodium, potassium. chlorine, water, urea, glucose, sucrose, polyethylene-glycol

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13
Q

Give some examples of substances which cannot pass through the glomerular barrier.

A

Haemoglobin
Serum albumin

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14
Q

There are three layers of filtration in the glomerular membrane.
What are the three layers?

A
  1. Fenestration of endothelial cells
  2. Basal lamina of glomerulus
  3. Slit membrane between pedicels
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15
Q

What is the function of the fenestration of endothelial cells as a filter layer?

A

Prevents filtration of blood cells but allows all components of blood plasma to flow in

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16
Q

What is the function of the basal lamina as a filter layer?

A

Prevents filtration of larger proteins

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17
Q

What is the function of the slit membrane as a filter layer?

A

Prevents filtration of medium size proteins

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18
Q

Describe the structure of afferent arterioles.

A

Short and wide

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19
Q

Describe the structure of efferent arterioles.

A

Long and narrow

-> think a before e in alphabet so longer way through alphabet, longer structure

20
Q

Why is glomerular capillary pressure higher than most of the other capillaries in the body?

A

Arrives in afferent arterioles which are short and wide and blood arriving at the glomerulus still has a high hydrostatic pressure

21
Q

Regarding the golden rule of circulation, what happens to hydrostatic pressure if there is high resistance?

A

Upstream- increased pressure
Downstream- decreased pressure

22
Q

Does hydrostatic pressure favour filtration or reabsorption?

A

Filtration

23
Q

Does oncotic pressure favour filtration or reabsorption?

A

Reabsorption

24
Q

What happens to oncotic and hydrostatic pressure as blood passes through the glomerulus?

A

Oncotic pressure increases but never exceeds high hydrostatic pressure

->as hydrostatic pressure favours filtration

25
Q

What is the only process which occurs at the glomerular capillaries?

A

Filtration

26
Q

What is the net filtration pressure?

A

10 mm Hg

-> this is because hydrostatic pressure is usually around the range of 55mmHg and then oncotic pressure (30mmHg) and fluid pressure (15mmHg) counteract so….
50-30-15=10

idk if that makes sense sorry gal

27
Q

In normal physiology, what affects glomerular filtration rate?

A

Afferent and efferent arteriolar diameter and the balance of resistance between them

28
Q

However, GFR can be affected by extrinsic factors like what?

A
  1. Sympathetic nerves
  2. Circulating catecholamines
  3. Angiotensin II
29
Q

Which are more sensitive to sympathetic nerves causing constriction; afferent or efferent arterioles?

A

Afferent

30
Q

Give some examples of catecholamines and what their function is.

A

Adrenaline, noradrenaline
Act as vasoconstrictors

31
Q

What role does angiotensin II have on GFR?

A

Vasoconstrictor which works at low concs. on efferents and high concs. on both efferent and afferent

32
Q

Renal vasculature also exhibits a well-developed intrinsic ability to adjust resistance in response to changes in arterial blood pressure.
This essentially keeps blood flow and GFR constant.
What is this known as?

A

Autoregulation

33
Q

Okayy imma reverse the question- what is autoregulation regarding filtration?

A

Renal vasculature has intrinsic ability to adjust resistance in response to changes in arterial blood pressure.
This essentially keeps blood flow and GFR constant.

34
Q

In humans, when BP is between 60-130, what happens to rate of glomerular filtration?

A

No changes as normal BP

35
Q

In humans, when BP is below 60, what happens to rate of glomerular filtration?

A

Filtration would decrease

->if under 50, filtration stops

36
Q

What happens if there is an increase in mean arterial pressure?

A

Automatic increase in afferent arteriolar constriction, preventing a rise of glomerular capillary pressure

->another form of autoregulation

37
Q

Does autoregulation depend on anything?

A

No, independent of nerves or hormones

->occurs in denervated and isolated perfused kidneys

38
Q

In situations where blood volume or pressure face serious compromise, e.g. haemorrhage, what happens?

A

Activation of sympathetic nerves and autoregulation can be overridden

->this means blood goes to more important organs

39
Q

However, while reduction in renal blood flow can supply organs with as much as 800ml /min, what happens if renal blood flow is reduced for a prolonged period of time?

A

Irreparable damage which can lead to death

40
Q

100% of plasma volume enters the glomerular capillaries via which type of arteriole?

A

Afferent arteriole

41
Q

20% of the plasma volume is filtered out, what happens to the rest?

A

Enters efferent arteriole and passes onto peritubular capillaries

42
Q

Out of 20% of plasma which is filtered out, how much is reabsorbed?

A

19%

43
Q

What happens to the 1% of plasma which is fiiltered?

A

Excreted

44
Q

Which type of capillary is responsible for reabsorption?

A

Peritubular capillaries

45
Q
A

Year 2- Urinary (22 decks)

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