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HUBS192 2024 > Lecture 31 - Glomerular function > Flashcards

Lecture 31 - Glomerular function Flashcards

1
Q

Filtration:

A

Movement of plasma from the glomerular capillaries (blood) into the glomerular capsule (nephron)

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2
Q

Most substances in plasma are freely-filtered meaning?

A

Not very selective at the glomerulus

Creates a plasma-like filtrate of the blood

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3
Q

What determines glomerular filtration?

A

Filtration barrier

Renal blood flow

Driving forces

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4
Q

Where does filtration occur?

A

Filtered into capsular space:

small substances (low molecular mass) are freely filtered

large substances (high molecular mass) are NOT filtered

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5
Q

What is renal blood flow equal to in the kidneys?

A

1/5th of CO per min

1100-1200mL blood/min

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6
Q

Why is high blood flow in the kidneys needed?

A

High flow for filtration, rather than metabolism

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7
Q

What are the two types of pressures?

A

Hydrostatic pressures

Pressure due to the volume of fluid
“Pushes” fluid away

Colloid osmotic pressures

Osmotic pressure due to protein
“Pulls” fluid towards

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8
Q

What are the 4 forces in the glomerulus?

A

Glomerular hydrostatic pressure (GHP),
Blood colloid osmotic pressure (BCOP),
Capsular hydrostatic pressure (CsHP),
Capsular colloid osmotic pressure (CsCOP)

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9
Q

What is Glomerular hydrostatic pressure (GHP) equal to?

A

+ 50 mmHg

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10
Q

What is Blood colloid osmotic pressure (BCOP) equal to?

A
  • 25 mmHg
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11
Q

What is Capsular hydrostatic pressure (CsHP) equal to?

A
  • 15 mmHg
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12
Q

What is Capsular colloid osmotic pressure (CsCOP) equal to?

A

0 mmHg, If damaged kidneys, there will be a pressure here

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13
Q

Proportion/percentage of the kidneys plasma flow is filtered is called?

A

Filtration fraction

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14
Q

Renal plasma flow :

A

45% of blood is cells

55% of blood is plasma

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15
Q

Filtration factor:

A

1/5th of the plasma which enters the kidneys (renal plasma flow) is filtered through the glomeruli into the nephrons

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16
Q

≈ 20% of the RPF is filtered in the?

A

glomerular capsule

nephron

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17
Q

≈ 80% remains in the glomerular capillaries

A

the efferent arteriole

peritubular capillaries

18
Q

GFR – Glomerular filtration rate

A

The amount of plasma filtered per unit time by the kidneys

19
Q

Renal plasma flow (RPF) x Filtration fraction (FF) =

A

Glomerular filtration rate (GFR)

20
Q

GFR = ? (mL/min)

A

125 mL/min

21
Q

RPF = ? (mL/min)

A

625 mL/min

22
Q

Glomerular filtration rate is?

A

Tightly regulated

Varies from person to person

Declines slowly from age 30

23
Q

Renal Filtered Load (RFL)

A

How much of a substance in the plasma is filtered per minute?

24
Q

Filtered Load =

A

the amount of a particular substance (solute) in the plasma is filtered per unit of time (per minute/hour/day)

= GFR x solute plasma conc.

25
Q

Renal Clearance

A

How much plasma is cleared of a substance per minute

26
Q

Clearance?

A

is the volume (mL) of plasma that is cleared of a substance by the kidneys per unit time (per minute)

27
Q

Clearance can be used to:

A

Quantify how a substance is handled by the kidneys

Estimate glomerular filtration rate (GFR)

28
Q

Creatinine and inulin are?

A

Freely filtered

Not secreted

Not reabsorbed

ALL filtered is excreted in urine

29
Q

Clearance of creatinine =

A

= Volume of plasma filtered per minute = GFR

30
Q

How much of creatinine is filtered?

A

20% of plasma filtered

Creatinine will be excreted in urine

31
Q

Medications and toxins (e.g. PAH) are?

A

Freely filtered

Entirely secreted

Not reabsorbed

ALL in blood is excreted in urine

32
Q

Clearance of PAH =

A

Volume of plasma flowing through the kidneys per minute = RPF

33
Q

How much of PAH is filtered?

A

20% of plasma filtered

ALL PAH which is filtered stays in the nephrons

PAH is entirely secreted so ALL PAH in the blood of the peritubular capillaries is secreted into the nephrons

This PAH will be excreted in the urine

34
Q

Glucose is?

A

Freely filtered

Not secreted

Fully reabsorbed in the proximal tubule

NONE excreted in urine
Except diabetes

35
Q

Clearance of Glucose =

A

NO plasma is cleared of glucose = 0

36
Q

How much of glucose is filtered?

A

NO glucose will be excreted in the urine

NO plasma has been “cleared” of glucose

37
Q

Sodium is?

A

Freely filtered

Not secreted

Almost fully reabsorbed in most parts of the nephron

Small amount excreted in urine

38
Q

Clearance of sodium =

A

Very small volume of plasma per minute

39
Q

How much of sodium is filtered?

A

A small amount of sodium is not reabsorbed

This sodium will be excreted in the urine

Almost all of the sodium which is filtered is reabsorbed

A small amount of the plasma which was filtered has been reabsorbed without sodium and has been “cleared” of sodium

40
Q

Clearance can be used to:

A

Quantify how a substance is handled by the kidneys

Estimate glomerular filtration rate (GFR)

Estimate renal plasma flow (RPF)

41
Q

To be used to measure GFR a substance must:

A

Be freely filtered

NOT be reabsorbed from the tubule

NOT be secreted into the tubule

42
Q

What two main substances meet the requirements to measure GFR?

A

Inulin and creatinine

HUBS192 2024 (38 decks)

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