L3:tubular structure and function Flashcards Preview

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Flashcards in L3:tubular structure and function Deck (71)
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1
Q

2 routes of transport for fluid moving from the tubule to the interstitial space

A
  • paracellular route

- transcellular route

2
Q

paracellular route=

A

between tight junctions, through lateral intercellular folds

3
Q

transcelluler route=

A

across apical, basolateral and translateral surfaces

4
Q

3 methods of transcellular transportation

A
  • primary active transport
  • secondary active transport
  • ion channels
5
Q

what is present on the apical membrane of cells to increase absorption

A

microvilli

6
Q

how much reabsorption happens in the PCT

A

2/3rd of nearly all filtrate

7
Q

how much glucose is reabsorbed in the PCT

A

100%

no glucose in urine

8
Q

what happens to glucose handling in diabetes mellitus

A

plasma glucose exceeds tubular maximum so glucosuria

9
Q

what is diabetes insipidus

A

problem with releasing ADH from pituitary gland, loss of salt and water

10
Q

what glucose transporter is on the apical membrane in early PCT

A

SGLT2

11
Q

what is SGLT2 affinity/capacity for glucose

A

high capacity

low affinity

12
Q

what glucose transporter is on the basolateral surface in the early PCT

A

GLUT-2

13
Q

apical glucose transporter in late PCT

A

SGTL-1

14
Q

basolateral glucose transporter in late PCT

A

GLUT-1

15
Q

SGLT-1 affinity/capacity for glucose

A

low capacity

high affinity

16
Q

at what point is glucose excreted into filtrate not reabsorbed

A

when levels pass the tubular transport maximum

17
Q

what effect does glycosuria have on urination

A
polyria 
and polydipsia (thirst)
18
Q

how are AA reabsorbed

A

98% via transcellular route in PCT

19
Q

how are AA filtered in the glomerulus

A

freely filtered

20
Q

were are small peptides reabsorbed

A

all reabsorbed in PCT

21
Q

how are small peptides reabsorbed

A

hydrolysed by brush border peptidases on apical membrane and reabsorbed as AA

22
Q

what percentage of proteins enter the filtrate

A

1%

23
Q

how are proteins reabsorbed

A

protein is endocytosed at apical membrane by peptide transporters

24
Q

the peptide transporters for protein reabsorption

A

PepT1

PepT2

25
Q

PepT1 capacity/ affinity=

A

high capacity

low affinity

26
Q

PepT2 capacity/affinity

A

low capacity

high affinity

27
Q

what happens to proteins in endosome

A

lysozymes join and hydrolyse protein into AA

28
Q

2 secretions of the PCT

A

organic anions

organic cations

29
Q

2 organic cations

A

creatinine

drugs

30
Q

3 drug cations secreted in PCT

A

trimethoprim
cimetidine
quinidine

31
Q

symporter=

A

substances go in same direction

32
Q

antiporter=

A

substances go in opposite direction

33
Q

amount of Na reabsorbed in PCT

A

70%

34
Q

what percentage of Na+ is secreted per day

A

0.4%

35
Q

main route of Na+ reabsorption

A

transcellular route

36
Q

what pump drives Na+ into the interstitial space

A

Na-K-ATPase

37
Q

how is Cl- reabsorbed

A

paracellularly driven by electrical gradient created by Na+ reabsorption

38
Q

osmolarity of fluid in beginning of loop of henle

A

isotonic with plasma

39
Q

as fluid descends down loop of henle what is the fluid movement

A

water moves out into interstitium

40
Q

what happens to osmolarity of fluid in loop of henle as you move down

A

becomes hypertonic (osmolarity increases)

41
Q

what substance movement happens in the ascending loop

A

Na/K/Cl actively pumps ion out of fluid into interstitium

42
Q

osmolarity of fluid in ascending loop=

A

hypotonic

43
Q

osmolarity of fluid in DCT

A

hypotonic

44
Q

what pumps do loop diuretics effect

A

Na/Cl/K co-transporter decreasing ion transport moving into blood

45
Q

e.g of loop diuretic

A

furosemide

46
Q

in DCT what channels does Na move through on apical membrane

A

ENaC epithelial sodium channel

47
Q

where do thiazides act

A

DCT

48
Q

what pump do thiazides work on

A

Na/Cl/K

49
Q

2 types of collecting ducts

A

cortical

medullary

50
Q

what happens in principal cells of cortical

A

sodium reabsorption via ENaC on apical and potassium channels

51
Q

what drug blocks ENaC

A

amiloride

52
Q

2 Na+ retaining factors

A
  • renin
  • sympathetic nervous system
  • vasopressin
53
Q

Na+ losing factor

A

-atrial natriuretic peptid

54
Q

what causes an increase in atrial natriuretic peptide release

A

increase in blood pressure

55
Q

atrial natriuretic peptide effect=

A

inhibits reabsorption of sodium –> decreasing Bp

56
Q

3 things that act on arterioles to lose Na+

A
  • Dopamine
  • Bradykinin
  • prostaglandins
57
Q

main site of Cl reabsorption

A

PCT -65%

58
Q

% of Cl reabsorbed in TAL

A

25%

59
Q

main site of magnesium reabsorption

A

thick ascending loop

60
Q

how is Mg reabsorbed

A

paracellularly

61
Q

what increases phosphate excretion

A

PTH

62
Q

main site of phosphate reabsorption

A

PCT

63
Q

what makes the collecting ducts more permeable to reabsorb water

A

ADH

64
Q

what substance move out of the collecting duct into interstitium to maintain conc

A

urea

65
Q

where is blood osmotic pressure detected

A

osmoreceptors in hypothalamus

66
Q

what receptors does ADH work on

A

v2 receptors in cortical collecting ducts

67
Q

where is aldosterone released from

A

zona glomerulosa in adrenal glands

68
Q

what does aldosterone bind to

A

MR (mineralocorticoid receptor

69
Q

3 things aldosterone-MR increases

A
  • ENaC
  • K+ channels on apical membrane
  • increase in basolateral Na/K/ATPase pump
70
Q

2 reasons aldosterone is released

A

Ang 2

increase K+ levels

71
Q

2 K+ sparring diuretics

A

spironalactone

amiloride