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MET 2 > Renal excretory function of kidney > Flashcards

Renal excretory function of kidney Flashcards

1
Q

How many litres go through the kidney

A

180

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2
Q

How many litres are lost as urine

A

2

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3
Q

Describe the structure of the glomerulus from venous inward

A

Venous
Porous endothelium
Glomerular basement membrane
Podocytes (epithelial surface)

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4
Q

What gets through podocytes

A

Glucose
Water
Solutes
Low molecular weight proteins

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5
Q

Where does filtration begin

A

Ultrafiltration of plasma within Bowmans Capsule

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6
Q

Name the factors that determine filtrate

A
  • Net filtration pressure
  • Podocyte slit pores
  • Size of molecule
  • Charge of molecule
  • Negative charge of GBM glycoproteins
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7
Q

What can get through the glomerulus

A

Water
Electrolytes
Urea
Amino

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8
Q

What is the cutoff of what can get through glomerulus

A

5200 daltons

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9
Q

What is the molecular weight of albumin? Can it get through?

A

69,000 daltons

No

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10
Q

What does albuminuria indicate

A

Problem at point of glomerulus because albumin shouldn’t be able to filter through

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11
Q

Define glomerular filtration rate

A

Total amount of fluid that is filtered through the glomeruls

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12
Q

What should normal GFR be

A

120ml/ min

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13
Q

What substance is used to measure GFR

A

Creatinine

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14
Q

Why is creatinine used to measure GFR

A
  • Freely filtered by glomerulus and is not reabsorbed
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15
Q

Why is measuring creatinine for GFR not accurate

A

It overestimates true renal function from 10-20% because it is actively secreted from peritubular capillaries

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16
Q

Equation for creatinine clearance

A

(urine concentration * urine volume)/ plasma concentration

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17
Q

Method for measuring clearance of a substance

A
  • Measure concentration of creatinine in the plasma
  • Collect urine for fixed period to get urine flow
  • Measure concentration of creatinine in the collected urine
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18
Q

What is the gold standard for measuring GFR

A

Nuclear medicine scan

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19
Q

What is commonly used to measure GFR

A

Estimated GFR

mdrd equation

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20
Q

What is required for MDRD equation

A

Sex
Age
Creatinine
Race

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21
Q

What shape is the curve on the graph showing relationship between GFR and creatinine

A

Bell shaped

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22
Q

What does the graph on the relationship between GFR and creatinine tell us

A
  • Small changes in creatinine have large affect on GFR

- Large changes in creatinine have small effect on GFR

23
Q

Why do muscular individuals have high serum creatinine

A

Because creatinine is produced by the muscle

24
Q

Does eGFR over or underestimate true GFR in

a) muscular people
b) malnourished people

A

a) underestimate

b) overestimate

25
Q

What is the use of the drug trimethoprin? What is the effect on plasma creatinine?

A

UTI treatment

Inhibits creatinine secretion from the peritubular capillary cells

26
Q

Does the drug trimethoprin change GFR

A

No

27
Q

What is the function of tight junction between tubular cells

A

Limits water and solute movement between cells

Maintains polarity between apical and baso-lateral

28
Q

Where does primary active transport occur

A

Between tubular cell and interstitium

29
Q

What is primary active transport pump

A

Na+/K+ pump

30
Q

What is the sodium and potassium levels in tubular cell

A

10-20mmol/l sodium

140mmol/l potassium

31
Q

What is the sodium and potassium levels in the interstitium?

A 
Na= 140mmol/L
Potassium= 4mmol/L
32
Q

Where does secondary active transport occur?

A

On the basolateral end of tubular cell

33
Q

What is pumped from tubular lumen to tubular cell in secondary active transport

A

Sodium
Phosphate
Glucose
Amino Acids

34
Q

Describe the anatomy of the proximal tubule

A

Apical brush border contains microvilli

It is convuluted for the first two thirds and straight for the final third

35
Q

What is the function of the proximal tubule

A

Bulk of reabsorption of solutes

36
Q

What % of the following are reabsorbed at proximal tubule

a) solutes
b) water
c) amino acids

A

a) 80
b) 65
c) 100

37
Q

How does sodium leave the loop of henle

A

Active transport

38
Q

What leaves through the ascending loop

A

Water

39
Q

How does osmolality change down the loop of henle

A

It increases

40
Q

Is the ascending limb permeable to water

A

No

41
Q

What does the distal nephron consist of

A

Distal tubule
Collecting tubule
Collecting duct

42
Q

What is the function of the distal nephron

A

Potassium excretion
Regulation of sodium delivery
Urine acidification

43
Q

How much sodium is left in filtrate when it reaches distal tubular cell

A

8%

44
Q

What inhibits the sodium potassium cell at distal tubular cells

A

Thiazide diuretics

45
Q

What determines the osmalality of urine in collecting tubule

A

ADH

46
Q

What happens in the presence of ADH

A
  • Aquaporins become permeable to water
  • Passage of water from collecting tubule to interstitium down conc gradient
  • Production of concentrated urine
47
Q

What happens if there is a deficit of ADH secretion

A

Copious dilute urine

Diabetes insipidus

48
Q

Define renal threshold

A

Concentration of substance dissolved in blood above which kidney begin to remove it into the urine

49
Q

What happens when the renal threshold is exceeded

A

Reabsorption of substance by proximal renal tubule is incomplete and some of substance remains in the urine

50
Q

What happens at plasma levels of about 10 mmol/L

A

Glucose appears in the urine because amount of glucose exceeds reabsorption capacity of tubules (all glucose carriers are saturated)

51
Q

Define transport maximum for glucose/ Tmg

A

Constant maximal value of rate of glucose reabsorption

52
Q

Define osmotic diuresis

A

If excess solute present in tubular fluid this will atrract water and increases urine volume

53
Q

What does osmotic diuresis lead to

A

Polyuria

54
Q

Why do diabetic people often complain of increased thirst

A

Polyuria leads to increase in plasma osmolality leading to thirst sensation

MET 2 (32 decks)

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