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Kidneys > Ultrafiltration and Glomerular filtration Rate > Flashcards

Ultrafiltration and Glomerular filtration Rate Flashcards

1
Q
  1. what percentage of blood is plasma?
A

55%

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2
Q
  1. How much blood do kidneys receive every minute and therefore how much plasma is filtered every minute?
A
  • receive ~1.25L blood/min
  • therefore 625ml/min of plasma is filtered
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3
Q
  1. What are the three basic renal processes?
A
  1. Glomerular filtration
  2. Tubular reabsorption
  3. Tubular Secretion
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4
Q
  1. Define glomerular filtration.
A

the transfer of fluid and solutes from the glomerular capillaries along a pressure gradient into Bowman’s capsule

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5
Q

define tubular reabsorption

A

selective movement of filtered substances from the tubular lumen into the peritubular capillaries

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6
Q

define tubular secretion

A

selective movement of non filtered substances from the peritubular capillaries into the tubular lumen

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7
Q
  1. What percentage and therefore amount in ml of plasma is filtered in each filtration cycle?
A

20% AKA 125ml/min

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8
Q
  1. What is the glomerular filtration rate?
A

the rate at which plasma is filtered by both kidneys

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9
Q
  1. How can the glomerular filtration rate be expressed numerically?
A

120 + or - 25ml/min/1.73m^2

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10
Q
  1. What are the 3 filtration layers of the glomerular filtration barrier?
A
  1. the fenestrated endothelium
  2. Glomerular basement membrane
  3. Podocytes
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11
Q
  1. What does kD mean in unit of measure?
A

a kilodalton

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12
Q
  1. What is filtered into the tubules where it is is then excreted?
A

plasma and anything < 70kD

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13
Q
  1. What stays in the blood and is not filtered? Give examples as well.
A

Anything > 70kD stays in the blood

  • Examples: Immunoglobulins, Ferritin, Cells, Plasma Proteins
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14
Q
  1. Why can’t albumin be filtered?
A
  • Because it is negatively charged
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15
Q
  1. What 4 forces, in order, are responsible for driving ultrafiltration?
A
  1. Glomerular blood hydrostatic pressure
  2. Capsular hydrostatic pressure
  3. Blood colloid osmotic pressure
  4. Net filtration Pressure
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16
Q
  1. What is the value and units for Glomerular blood hydrostatic pressure?
A

55 mmHg

17
Q
  1. What is the value and units for capsular hydrostatic pressure?
A

15 mmHg

18
Q
  1. What is the value and units for blood osmotic pressure
A

30 mmHg

19
Q
  1. What is the normal value and units for Net filtration pressure?
A

10 mmHg

20
Q
  1. How is net filtration pressure calculated?
A

NFP = GBHP - CHP - BCOP

21
Q
  1. Does GFR change when blood pressure changes?
A

No

22
Q
  1. What is the definition of autoregulation?
A

the ability of a tissue to automatically adjust its blood flow to match its metabolic demands without nerves or hormones

23
Q
  1. What 2 ways is negative feedback achieved in autoregulation of renal blood flow?
A
  1. Tubuloglomerular feedback
    2.Myogenic control
24
Q
  1. What is Tubuloglomerular feedback
A

When tubular flow rate is detected by the macula densa & vasoactive mediators are released from the JGA to act on the arterioles.

25
Q

what do the chemicals do in tubular feedback

A

The chemicals dilate or constrict the afferent arteriole as needed to keep the GFR within normal range

26
Q
  1. Give examples of vasoactive mediators that 1. Vasocontrict 2. Vasodilate that are released from the JGA in Tubuloglomerular feedback
A

Vasoconstrict:
- Angiotension II & endothelin

Vasodilate:
- Atrial natriuretic peptide, prostaglandins nitric oxide

27
Q
  1. What is myogenic control?
A

The afferent or efferent arteriolar
diameter automatically increases
or reduces to oppose pressure changes

28
Q
  1. What mean arterial pressure range is the GFR autoregulated at
A

80-180mmHg

29
Q
  1. How do the efferent and afferent arterioles constrict?
A

sympathetic nerves which constrict the vessels via α1adrenoceptors

30
Q
  1. What does constriction of the efferent and afferent arterioles do?
A

reduces plasma flow to the glomerular filter and slows filtration. This means less is excreted. This conserves plasma in the circulation to help maintain blood pressure.

31
Q

what 2 ways can tubuloglomerular feedback and myogenic control be reduced

A

Pathological conditions
- Glomerulopathies
- E.g. immune complexes, toxins,
- Inherited disease

Non-pathological conditions
Pregnancy, kidney removal, ageing
GFR may be reduced

Kidneys (7 decks)

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