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Flashcards in Urinary Session 3 Deck (66):
1

What do the efferent arterioles in cortical nephrons drain into?

Peritubular capillaries

2

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

Afferent>efferent

3

What does the efferent arteriole of juxtamedullary nephrons drain into?

Vasa recta

4

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

Cortical have rich supply, juxtamedullary have poor supply

5

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

High in cortical, almost none in juxtamedullary

6

Where are cortical nephrons located?

Outer cortex

7

Where are juxtamedullary nephrons found?

Inner part of cortex

8

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

Smaller in cortical

9

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

20%

10

Does the proportion of blood filtered depend on the nephron?

No

11

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

90% cortical
10% medullary

12

What does the permeable capillary endothelium allow between cells?

Water
Salts
Glucose

13

What repels protein movement in the basement membrane?

-ve charge acellular gelatinous collagen/glycoprotein basement membrane

14

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

Interdigitation of pseudopodia of podocytes

15

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

Inulin

16

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

They have a negative charge

17

What causes proteinuria?

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

18

What are the three forces in plasma filtration?

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

19

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

Autoregulation of hydrostatic pressure in the capillary

20

What is the myogenic response to small increases in BP?

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

21

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

No smooth muscle stretch --> afferent arteriole dilation

22

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

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

23

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

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

24

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

When BP is within physiological limits

25

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

Using concentration dependent uptake through NaK2Clco transporters in the apical membrane

26

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

Adenosine or prostaglandins

27

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

Cortical
Juxtamedullary

28

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

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

29

Why does bulk transport/isosmotic occur in the PCT?

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

30

How can reabsorption occur?

Transcellular
Paracellular

31

Which type of reabsorption is predominantly used?

Transcellular

32

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

Na-H antiporter
Na-glucose symporter

33

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

Na-K-2Cl symporter

34

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

NaCl symporter

35

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

ENaC

36

What is the end result of reabsorption?

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

37

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

Secretion

38

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

H+
K+
Organic anions

39

Describe the process of secretion into the tubular lumen.

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

Why do cations compete to be transported?

Due to Tm limitation

41

How do cations enter and exit luminal cells?

Enter on basolateral side by one of several uniporters
Leave via H+ antiporter in apical membrane

42

Give some examples of endogenous cations.

ACh
Dopamine
Adrenaline
Histamine
Serotonin

43

Give some examples of drugs which are cations.

Sulfonamides
Morphine
Atropine
Isoproterenol

44

Give some examples of endogenous anions.

Urate
Bile salts
Fatty acids

45

Give some examples of drugs that are anions.

Penicillin
Salicylate
NSAIDs

46

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

That administered drugs will be secreted by the kidneys

47

What is the normal range of GFR for males?

115-125 ml per minute

48

What is the normal GFR range for females?

90-100 per minute

49

What is the benchmark measure of kidney health?

GFR

50

What characteristics does a substance used to measure GFR require?

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

51

Can a standalone GFR be used to assess kidney health?

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

52

What ultimately governs GFR?

Renal blood flow

53

What is the normal renal blood flow through the glomeruli?

~1.1 l per minute

54

What percentage of renal blood flow is haematocrit?

Usually 45%

55

What is normal renal plasma flow?

605 ml per min (0.55x1.1)

56

What is renal clearance?

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

57

How is renal clearance calculated?

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

58

What is renal clearance used to detect?

Glomerular damage
Follow progress of diagnosed renal disease
Determine GFR

59

What is the gold standard for measuring renal clearance?

Inulin

60

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

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

61

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

A small amount is secreted

62

What does eGFR account for?

Age affecting kidney function
Mass affecting creatinine levels

63

What is the Tm of glucose in males and females?

Males = 375 mg per minute
Females = 300 mg per minute

64

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

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

What is normal plasma glucose concentration?

~1 mg per ml

66

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

Yes