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Semester 3 > Urinary Session 3 > Flashcards

Urinary Session 3 Flashcards

1
Q

What do the efferent arterioles in cortical nephrons drain into?

A

Peritubular capillaries

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2
Q

How does the diameter of the efferent and afferent arterioles compare in cortical nephrons?

A

Afferent>efferent

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3
Q

What does the efferent arteriole of juxtamedullary nephrons drain into?

A

Vasa recta

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4
Q

How does the sympathetic supply of cortical and juxtamedullary nephrons compare?

A

Cortical have rich supply, juxtamedullary have poor supply

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5
Q

How does the renin concentration in cortical and juxtamedullary nephrons compare?

A

High in cortical, almost none in juxtamedullary

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6
Q

Where are cortical nephrons located?

A

Outer cortex

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7
Q

Where are juxtamedullary nephrons found?

A

Inner part of cortex

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8
Q

How does the size of the glomerulus compare in cortical and juxtamedullary nephrons?

A

Smaller in cortical

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9
Q

What proportion of blood flow is filtered at any one time?

A

20%

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10
Q

Does the proportion of blood filtered depend on the nephron?

A

No

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11
Q

What is the ratio of cortical to juxtamedullary nephrons in the kidney?

A

90% cortical

10% medullary

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12
Q

What does the permeable capillary endothelium allow between cells?

A

Water
Salts
Glucose

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13
Q

What repels protein movement in the basement membrane?

A

-ve charge acellular gelatinous collagen/glycoprotein basement membrane

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14
Q

What determines the size of particles that can move through the filtration barrier?

A

Interdigitation of pseudopodia of podocytes

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15
Q

What is the largest molecule that can pass through the filtration barrier?

A

Inulin

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16
Q

Why do some smaller proteins not pass through the filtration barrier?

A

They have a negative charge

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17
Q

What causes proteinuria?

A

Loss of -ve charge on the basement membrane so proteins are more readily filtered

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18
Q

What are the three forces in plasma filtration?

A

Hydrostatic pressure in the capillary
Hydrostatic pressure in the Bowman’s capsule
Oncotic pressure difference between capillary and tubular lumen

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19
Q

What allows GFR to remain constant during small fluctuations in BP?

A

Autoregulation of hydrostatic pressure in the capillary

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20
Q

What is the myogenic response to small increases in BP?

A

Increased BP –> stretch afferent arteriole smooth muscle –> smooth muscle contacts to decrease blood flow

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21
Q

What is the myogenic response to small decreases in blood pressure?

A

No smooth muscle stretch –> afferent arteriole dilation

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22
Q

What is the response via tubular-glomerular feedback to a small increase in BP?

A

Increased BP –> increased GFR –> increased tubular flow rate –> increased sodium and chloride concentrations detected by macula densa cells –> adenosine release

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23
Q

What is the tubular-glomerular feedback response to a small decrease in BP?

A

Decreased sodium and chloride concentrations detected by macula densa cells –> prostaglandin release

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24
Q

When do the myogenic and tubular-glomerular feedback responses maintain GFR?

A

When BP is within physiological limits

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25
Q

How do macula densa cells sense luminal sodium and chloride concentration?

A

Using concentration dependent uptake through NaK2Clco transporters in the apical membrane

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26
Q

What do macula densa cells stimulate the release of to control afferent arteriole vasomotor tone?

A

Adenosine or prostaglandins

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27
Q

What are the two types of nephrons found in the kidneys?

A

Cortical

Juxtamedullary

28
Q

Why is movement of solutes and water in the nephron classed as reabsorption?

A

Substances have a already been absorbed into the blood once (especially in the intestines)

29
Q

Why does bulk transport/isosmotic occur in the PCT?

A

Polarised tubule cells drive sodium uptake and other ions follow to maintain electro-neutrality

30
Q

How can reabsorption occur?

A

Transcellular

Paracellular

31
Q

Which type of reabsorption is predominantly used?

A

Transcellular

32
Q

Which sodium transporters in the apical membrane of PCT cells are targeted by diuretics?

A

Na-H antiporter

Na-glucose symporter

33
Q

Which sodium transporter in the apical membrane of Loop of Henle epithelial cells is targeted by diuretics?

A

Na-K-2Cl symporter

34
Q

Which sodium transporter in the apical membrane of early distal tubule epithelial cells is targeted by diuretics?

A

NaCl symporter

35
Q

Which sodium transporter in the apical membrane of late DCT and collecting duct epithelial cells is targeted by diuretics?

A

ENaC

36
Q

What is the end result of reabsorption?

A 
Reabsorption of:
100% filtered nutrients
80-90% filtered HCO3-
67% filtered Na+
65% filtered water
65% filtered Cl-
65% filtered K+
37
Q

What provides a second route of entry for solutes that need to be secreted into the tubular fluid?

A

Secretion

38
Q

What in the 80% of unfiltered plasma needs secretion into the tubule?

A

H+
K+
Organic anions

39
Q

Describe the process of secretion into the tubular lumen.

A

3Na-2K-ATPase creates concentration and electrochemical gradient
Entry of molecules by passive carrier-mediated diffusion down gradients
Na-H antiporter creates H+ gradient
H+-OC+ exchanger pumps in H+ to restore balance and in the process pumps OC+ into lumen

40
Q

Why do cations compete to be transported?

A

Due to Tm limitation

41
Q

How do cations enter and exit luminal cells?

A

Enter on basolateral side by one of several uniporters

Leave via H+ antiporter in apical membrane

42
Q

Give some examples of endogenous cations.

A 
ACh
Dopamine
Adrenaline
Histamine
Serotonin
43
Q

Give some examples of drugs which are cations.

A

Sulfonamides
Morphine
Atropine
Isoproterenol

44
Q

Give some examples of endogenous anions.

A

Urate
Bile salts
Fatty acids

45
Q

Give some examples of drugs that are anions.

A

Penicillin
Salicylate
NSAIDs

46
Q

What must be considered when choosing a drug and calculating dosages?

A

That administered drugs will be secreted by the kidneys

47
Q

What is the normal range of GFR for males?

A

115-125 ml per minute

48
Q

What is the normal GFR range for females?

A

90-100 per minute

49
Q

What is the benchmark measure of kidney health?

A

GFR

50
Q

What characteristics does a substance used to measure GFR require?

A

Not altered in any way in the nephron
Freely filtered
Not secreted

51
Q

Can a standalone GFR be used to assess kidney health?

A

No, needs a series of measurements to see where a pt’s normal GFR is

52
Q

What ultimately governs GFR?

A

Renal blood flow

53
Q

What is the normal renal blood flow through the glomeruli?

A

~1.1 l per minute

54
Q

What percentage of renal blood flow is haematocrit?

A

Usually 45%

55
Q

What is normal renal plasma flow?

A

605 ml per min (0.55x1.1)

56
Q

What is renal clearance?

A

Volume of plasma that is completely cleaned of a substance by the kidneys per unit time

57
Q

How is renal clearance calculated?

A

(Concentration of substance in urine X urine volume)/concentration of it in plasma

58
Q

What is renal clearance used to detect?

A

Glomerular damage
Follow progress of diagnosed renal disease
Determine GFR

59
Q

What is the gold standard for measuring renal clearance?

A

Inulin

60
Q

What substance is used clinically to measure renal clearance and why?

A

Creatinine as it doesn’t have to be given IV like inulin

61
Q

Why does using creatinine give a slight overestimate of renal clearance?

A

A small amount is secreted

62
Q

What does eGFR account for?

A

Age affecting kidney function

Mass affecting creatinine levels

63
Q

What is the Tm of glucose in males and females?

A 
Males = 375 mg per minute
Females = 300 mg per minute
64
Q

What happens if plasma glucose concentration is 400 mg per ml in a male?

A

Filtered load is 4x125 = 500 mg per minute

As renal threshold is 375 mg per minute 125 mg per minute moves into the urine

65
Q

What is normal plasma glucose concentration?

A

~1 mg per ml

66
Q

Is normal plasma glucose concentration freely filtered in the Bowman’s capsule?

A

Yes

Semester 3 (50 decks)

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