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FBS1 > PPP- kidneys > Flashcards

PPP- kidneys Flashcards

1
Q

What products does the kidney produce?

A

renin, vitamin D, erythropoietin, prostaglandins and alpha-klotho

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2
Q

What does the renal corpuscle consist of?

A

glomerulus and bowman’s capsule

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3
Q

What type of endothelium is in the glomerulus capillaries?

A

fenestrated

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4
Q

What are the slit proteins in podocytes?

A

nephrin and podocin

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5
Q

What does the renal tubule drain into?

A

renal pelvis

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6
Q

What are the different types of nephron?

A

cortical - 85%

juxtamedullary - 15%

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7
Q

What is the difference between cortical and juxtamedullary nephrons?

A

cortical are in outer 2/3rds of cortex & have a short loop of henle

Juxtamedullary are in the inner 1/3rd & have a long loop of henle

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8
Q

What are the contents of the juxtamglomerular apparatus?

A
  • Juxtaglomerular cells
  • macula densa cells
  • mesangial cells
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9
Q

What is the vasa recta

A

capillaries that run parallel to the loop of henle

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10
Q

How do you calculate the amount of a substance in urine?

A

amount filtered + amount secreted - amount reabsorbed

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11
Q

Name a substance that is filtered and secreted but not reabsorbed?

A

PAH

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12
Q

Name a substance that is filtered and partially reabsorbed?

A

water and electrolytes

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13
Q

Name a substance that is filtered and completely reabsorbed?

A

glucose

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14
Q

What substance isn’t freely filtered in the glomerulus?

A

proteins

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15
Q

What does glomerular filtration depend on?

A

molecular size and charge

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16
Q

What would a plasma:filtrate ratio of 1 mean?

A

the substance is freely filtered

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17
Q

How does charge affect filtration?

A

basement membrane is negatively charged, so attracts cations

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18
Q

What can cause proteinuria, haemogloinuria and haematuria?

A

infection, glomerulus damage and very high BP

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19
Q

What does GFR mean?

A

the volume of fluid filtered per minute

- ml/min

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20
Q

What is the normal GFR?

A

125ml/min

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21
Q

What does GFR depend on?

A
  • starling forces
  • surface area
  • hydraulic permeability of capillaries
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22
Q

What is the net pressure in the glomerulus due to starling forces?

A

16mmHg

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23
Q

What are starling forces?

A

opposing hydrostatic and oncotic pressure

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24
Q

How can surface area of the glomerulus be controlled?

A

mesangial cells contains actin which is contracted in low BP to reduces SA -> reduces GFR

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25
Q

What effect does constricting afferent arteriols or dilating efferent arterioles have?

A

reduces GFR

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26
Q

What is the normal urine output?

A

1.5L/day

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27
Q

What features does the proximal tubule have for reabsorption?

A
  • brush border
  • folds in epithelium
  • lots of mitochondria
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28
Q

Where does most reabsorption occur?

A

in the proximal tubule

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29
Q

How is glucose reabsorbed?

A
  • energy comes from Na/K pump
  • Glucose enters cell via Na co-transport
  • enters lumen via GLUT transporters
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30
Q

What is the renal threshold for glucose filtration?

A

plasma conc of 200mg

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31
Q

What happens if glucose conc is above the renal threshold?

A

no more glucose is reabsorbed as all the Na co-transporters are saturated

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32
Q

How are amino acids rebsorbed?

A

in the proximal tubule by specific transporters

  • 8 different types
  • 6 are Na+ dependent
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33
Q

How are acids/anions secreted?

A
  1. enter cells in exchange for DC- via OAT1/3

2 enter lumen via ATP-dependent transporters

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34
Q

What are some secreted acids/anions?

A

bile salts, fatty acids, prostaglandins, drugs, PAH

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35
Q

How are bases/cations secreted in the proximal tubule?

A
  1. enter cell via OCT2 facilitated diffusion

2. enter lumen in exchanged for H+ via MATE antiporters

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36
Q

What are some secreted bases/cations?

A

creatinine, dopamine, choline, adrenaline, histamine, atropine, morphine, cimetidine

37
Q

What is the formula for renal clearance?

38
Q

What is renal clearance?

A

volume of plasma cleared of a substance in a given time

39
Q

Why is inulin used to measure clearance experimentally?

A
  • exogenous
  • not absorbed or secreted
  • not metabolised
  • easily measured
40
Q

What is used to measure clearance clinically?

A

creatinine

41
Q

what does a clearance of >120ml/min indicate?

A

the substance is secreted

42
Q

what does a clearance of <120ml/min indicate?

A

the substance is reabsorbed

43
Q

What is the effective renal plasma flow?

44
Q

what is renal blood flow?

A

600/0.55 = 1100ml/min

- 25% of CO

45
Q

how do you calculate renal blood flow?

A

plasma flow/1-haematocrit

46
Q

What is the osmolality of plasma?

A

285-295mosm/L

47
Q

What is the osmolality of urine?

A

50-1400 mosm/L

48
Q

What is the main osmotically active solute?

49
Q

Where does sodium reabsorption occur?

A

mainly in proximal tubule and thick ascending limb

  • passive in thin ascending
  • none in descending limb
50
Q

How is sodium reabsorbed in the proximal tubule?

A

via Na-H+ exchanger and Na-glucose symporter

51
Q

How is sodium reabsorbed in the thick ascending limb?

A

NKCC transporter

- creates positive charge in lumen -> paracellular cation movement

52
Q

How is sodium reabsorbed in the distal tubule?

A

Na-Cl cotransporter

53
Q

How is sodium reabsorbed in the collecting duct?

A

ENaC channel

54
Q

How is urea recycled by the kidneys?

A
  1. passive reabsorption in proximal tubule -> 50% of original
  2. secreted by UT-A2 in LOH -> 110% of original
  3. reabsorbed by UT-A1 in collecting ducts -> 40% of original
55
Q

How does ADH control water reabsorption?

A

binds basolateral V2 receptors
causes insertion of AQA-2 on luminal side
Water moves out of cell by constitutively active AQP3/4

56
Q

How is ADH released?

A

released from posterior pituitary when plasma osmolality is increased (dehydration)

57
Q

Where are the osmoreceptors that signal ADH release?

A

hypothalamus

58
Q

What 2 factors maintains plasma osmolality?

A

urine formation and thirst

59
Q

What is the obligatory water loss per day?

60
Q

What is oliguria?

A

when urine output is less than the obligatory water loss

61
Q

What is the max urine output?

62
Q

How is osmolar clearance calculated?

A

(Uosm x V)/Posm

63
Q

What is osmolar clearance?

A

the clearance of all osmotically active particles

64
Q

what is the fasting osmolar clearance?

65
Q

How do you calculated free water clearance?

A

V - (Uosm x V)/Posm

66
Q

What are the values of free water clearance?

A 
>0 = dilute urine
0 = isosmotic urine
<0 = concentrated urine
67
Q

What is the main control of ADH secretion?

A

osmolality

68
Q

What factors can control ADH?

A
  • osmolality (main)
  • blood volume/pressure (requires greater change)
  • Alcohol inhibits release
  • nicotine, pain and stress increase release
69
Q

What is diabetes insipidus characterised by?

A

polyuria, polydipsia and nocturia

70
Q

What are the 2 types of diabetes insipidus?

A

neurogenic and nephrogenic

71
Q

What can cause neurogenic diabetes insipidus?

A
  • no secretion of ADH

- congenital or by brain injury

72
Q

What can cause nephrogenic diabetes insipidus?

A
  • inherited mutation e.g. V2 receptor

- acquired by infection or lithium use

73
Q

What is osmotic diuresis characterised by?

A

polyuria and polydipsia

74
Q

What causes osmotic diuresis?

A
  • increased blood glucose
  • increases filtrate osmolarity
  • decreased water absorption in PT, later parts can’t compensate
75
Q

How is potassium levels maintained?

A
  • renal excretion
  • GI losses
  • cellular shifts
76
Q

How is K+ reabsorbed?

A
  • passivly in PT (65%)
  • by NKCC2 in thick ascending limb
  • K-H+ exchange in distal tubule
  • secreted in principle cells by ROMK and BK
77
Q

What factors affect principle cell K+ secretion?

A
  • ENaC factors
  • aldosterone (increases secretion)
  • tubular flow rate (rate increases secretion)
  • acidosis decreases secretion
    alkalosis increases secretion
78
Q

What are the concentrations of potassium in hypokalemia?

A 
mild = 3-3.5mM 
moderate = 2.5-3 mM 
severe = <2.5mM
79
Q

What can cause hypokalemia?

A
  • increased external loses
  • redistribution into cells
  • low intake
80
Q

What causes increased external loss of potassium?

A

diuretics, transporter mutations, hyperaldosteronism, alklaosis, vomitting, diarrhoea, skin burns, osmotic diuresis

81
Q

What causes redistribution of potassium into cells?

A

insulin excess and metabolic alkalosis

82
Q

What happens to the RMP in hypokalemia?

A

becomes more negative, so takes more to drive to threshold, and repolarises more slowly

83
Q

What concentration indicates hyperkalemia?

A

Plasma [K+] > 5.5mM

84
Q

What causes decreased external loss of potassium?

A

renal failure
hypoaldosterone
drugs

85
Q

What causes redistribution of potassium out of cells?

A

acidosis
cell lysis
tissue destruction

86
Q

What happens to the RMP in hyperkalemia?

A

increased, so more likely to depolarise

87
Q

Is polyuria seen in hyperkalemia or hypokalemia?

A

hypokalemia

88
Q

What is the treatment for hypokalemia?

A
  • Potassium rich foods
  • administration of KCl
  • use of K+ sparing diuretics
  • alkalosis correction
89
Q

What is the treatment for hyperkalemia?

A

short term: stabilise heart with Ca2+
medium term: insulin treatment to shift K+ into cells
long term: increase excretion with diuretics

FBS1 (9 decks)

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