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Urinary System > Glomerular Filtration > Flashcards

Glomerular Filtration Flashcards

1
Q

Where does filtration occur?

A

The glomerulus within the nephron

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2
Q

What is the function of filtration?

A

To excrete waste and excess fluid from the blood and maintain ECF volume

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3
Q

How much fluid does the kidney filter daily?

A

180l/day

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4
Q

How much blood do the kidneys recieve?

A

1200ml/min = 20-25% of cardiac output

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5
Q

What is the rate of renal plasma flow?

A

660 ml/min

55% x 1200 = 660

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6
Q

What is the Glomerular Filtration Rate?

A

125ml/min

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7
Q

What is the filtration fraction ?

A

125/660 = 19%

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8
Q

What is glomerular filtration dependent on?

A

Hydrostatic Forces and Osmotic Pressure

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9
Q

What do hydrostatic forces favour?

A

Filtration

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10
Q

What does osmotic pressure favour?

A

Reabsorption

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11
Q

What is the function of the glomerular endothelial cells?

A

To prevent filtration of blood cells but they do allow for plasma components to pass through

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12
Q

What is the function of the basal lamina of the glomerulus?

A

Prevents filtration of large proteins (prevents them from passing through)

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13
Q

What is the function of the slit membranes?

A

To prevent medium proteins from undergoing filtration

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14
Q

What does the afferent arteriole do?

A

Delivers blood to glomerulus

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15
Q

What does the efferent arteriole do?

A

Carries blood away from glomerulus

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16
Q

Why do arterioles change size?

A

To increase or decrease blood pressure in glomerulus

17
Q

Why is Glomerular Capillary Pressure (Pgc) higher than most capillaries?

A

As the afferent arteriole is short and wide and thus, resistance to blood flow is low.

Means that blood arriving at glomerulus has a high hydrostatic pressure

18
Q

What affect does the length and width of the efferent arteriole have on capillary resistance?

A

The long and narrow efferent arteriole results in a high post capillary resistance

19
Q

What does increased resistance do to hydrostatic pressure in the glomerulus?

A

High resistance = upstream hydrostatic pressure is high, downstream pressure is low

Low resistance = upstream pressure low, downstream pressure high

20
Q

How do sympathetic VC nerves affect GFR?

A

Afferent and efferent constriction is observed but there is greater sensitivity in afferent arteriole

21
Q

What effect do circulating catecholamines have on GFR?

A

Constriction occurs primarily in afferent arteriole

22
Q

How does angiotensin II affect GFR?

A

Constriction occurs in EFFERENT @ low concentration, in AFFERENT AND EFFERENT @ high concentration

23
Q

What is glomerular hydrostatic pressure equal to?

A

55mmHg

24
Q

What is Blood Colloid Osmotic Pressure equal to?

A

30mmHg

25
Q

What is Capsular Hydrostatic Pressure equal to?

A

15mmHg

26
Q

What is the net outward pressure of the glomerular filtration system?

A

10mmHg

55-30-15=10

27
Q

What occurs when there is an increased resistance in the afferent arteriole?

A

Increased Hydrostatic pressure, Decreased capillary blood pressure = decreased GFR

28
Q

What occurs when there is an increased resistance in the efferent arteriole?

A

Increased hydrostatic pressure = Increased GFR

29
Q

What occurs when there is a decreased resistance in the afferent arteriole?

A

There is an increase in hydrostatic pressure resulting in increased GFR

30
Q

What is the intrarenal auto-regulatory range in humans?

A

60-130mmHg

31
Q

What occurs when blood pressure drops to 60mmHg?

A

Filtration fails

32
Q

What occurs when blood pressure drops to 50mmHg?

A

Filtration stops

33
Q

How much fluid filtrated by the glomerulus is excreted as urine?

A

~1l

34
Q

Where is the majority of filtered products reabsorbed?

A

The peritubular capillaries

35
Q

Why do peritubular capillaries offer such a low hydrostatic pressure?

A

Resistance is present across whole tube = large pressure drop = low hydrostatic pressure of 15mmHg

LOW HYDROSTATIC PRESSURE IS NOT FAVOURABLE FOR FILTRATION

36
Q

What does an decrease in Ppc and an increase in πp result in ?

A

Favourable conditions for re absorption

Urinary System (15 decks)

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