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LSM3214 > Kidneys > Flashcards

Kidneys Flashcards

1
Q

Where do the glomerular capillaries supply?

A

Afferent to efferent arteries

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2
Q

Where do the peritubular capillaries supply?

A

Supplies blood to renal tubules

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3
Q

What is the glomerulus?

A

A ball of capillaries including the efferent and afferent arterioles that sits in the bowmans capsule

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4
Q

What is ultrafiltration?

A

When capillary contents is filtered into the bowmans capsule

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5
Q

What features does the capillary endothelium have to allow for ultrafiltration?

A

Fenestrations, which allow molecules to squeeze through

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6
Q

Where are podocytes?

A

In the glomerular basement membrane

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7
Q

What features do podocytes have to allow for ultrafiltration?

A

Pseudopodia filtration slits that prevents large, negative proteins from passing

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8
Q

Where are mesengial cells located?

A

Between 2 capilaries

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9
Q

What are the functions of mesengial cells?

A

Contractile and help regulate glomerular blood flow

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10
Q

Which parts of the nephron is in the cortex?

A

Bowmans capsule, proximal tubule, distal tubule

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11
Q

Which parts of the nephron is in the medulla?

A

Loop of henle, collecting duct

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12
Q

What is the function of the juxtaglomerular complex?

A

Regulate blood pressure, glomerular filtration and Na+ reabsorption

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13
Q

What cells are involved in the juxtaglomerular complex?

A

Macula densa cells of the initial portion of the distal tubule and juxtaglomerular cells in the afferent and efferent arterioles

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14
Q

What is the structure of the juxtaglomerular complex?

A

The afferent and efferent arterioles come into close contact with the distal tubule

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15
Q

What is the filtration and reabsorption features of inulin?

A

100% filtration, 0% reabsorption

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16
Q

What is the filtration and reabsorption features of glucose & amino acids?

A

100% filtration, 100% reabsorption

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17
Q

What happens to GFR when the capillary bed size increases?

A

Higher capillary bed size (mesengial cells relax) = higher GFR

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18
Q

What molecules are capillaries selectively against?

A

Negatively charged molecules, as the membrane itself is negatively charged!

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19
Q

Can any molecule diffuse across glomerular capillaries?

A

Yes, small molecules can

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20
Q

What is the equation for filtration fraction?

A

GFR/renal plasma flow

normal filtration fraction = 0.2

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21
Q

What happens to GFR if the efferent arteriole diameter decreases?

A

Low efferent arteriole diameter = lesser blood leaving = higher blood pressure = improved GFR

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22
Q

What happens to GFR if the afferent arteriole diameter increases?

A

Higher afferent arteriole diameter = higher blood flow = lower blood pressure = lower GFR

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23
Q

What occurs when the macula densa detects lower NaCl signals?

A
  • Renin secretion
  • Lower afferent arteriolar resistance
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24
Q

What is the clearance equation

A

(Substance A concentration in urine x urine flow)/substance A concentration in plasma

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25
Q

What does it mean if clearance > GFR?

A

Substance is secreted into renal tubules (i.e. excreted)

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26
Q

What does it mean if clearance < GFR?

A

Substance is reabsorbed into renal tubules

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27
Q

What is reabsorbed at the proximal tubule?

A

100% glucose + water!

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28
Q

What is the water permeability of the thin descending loop of henle?

A

Highly permeable to water - made of thin, small, metabolically inactive cells with no resorptive capacity

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29
Q

Can electrolytes be reabsorbed at the thin descending loop of henle?

A

Yes, only small amounts can diffuse and be reabsorpbed

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30
Q

What is the water permeability of the ascending loop of henle?

A

Impermeable to water - made of thick metabolically active cells with resorptive capacity

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31
Q

What is the ionic permeability of the ascending loop of henle?

A

Permeable to K, Cl, Na

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32
Q

What ion pumps are present at the ascending loop of henle?

A

Na+/K+ pump (3 Na+ reabsorbed, 2 K+ secreted)
NKCC2 cotransporter (all reabsorbed)

33
Q

What is the water and ionic permeability at the early distal tubule?

A

Impermeable to H2O but reabsorbs most ions

34
Q

What is the water permeability at the late distal tubule?

A

Reabsorbs water, controlled by ADH

35
Q

What occurs at the distal tubule?

A

K+ & H+ secretion

36
Q

What is the function of principal cells?

A

K+ secretion

37
Q

What is the function of intercalated cells?

A

H+ secretion, K+ & HCO3- reabsorption

38
Q

What is the water permeability at the collecting duct and what is it controlled by?

A

Permeability dependent on ADH!

39
Q

How is Na+ reabsorbed?

A

Movement coupled to H+, glucose etc. in co-transport/exchange

Subsequently pumped out in Na+ K+ ATPase

40
Q

How is glucose reabsorbed?

A

Reabsorbed with Na+ into tubular cells by SGLT
Transported into extracellular spaces/other cells by GLUT

41
Q

How is K+ secreted?

A

Secretion by principal cells stimulated by aldosterone

(More K+ = more aldosterone = more secretion)

42
Q

What are the 2 regulators of osmolality?

A

ADH and the countercurrent mechanism in the loop of Henle

43
Q

What is the function of ADH?

A

Promotes H2O reabsorption!

44
Q

What is the osmolality across the tubule with the action of ADH?

A

Osmolality starts at 300 at the proximal tubule, increasing to 1200 as water is reabsorbed at the descending loop of henle.

Osmolality decreases to 600 as solutes are reabsorbed and subsequently to 100 in the distal tubule as both H2O and water are reabsorbed.

Osmolality increases at the collecting duct as water is reabsorbed.

45
Q

What are countercurrent multipliers?

A

Descending and ascending loop of henles

46
Q

What are countercurent exchangers?

A

Vasa recta

47
Q

What is the vasa recta?

A

Peritubular capillaries that surround the loop of Henle.

48
Q

What is the countercurrent system?

A

A system in which the inflow runs parallel and counter to the outflow.

49
Q

What is the countercurrent mechanism to decrease vasa recta osmolality?

A

H2O leaves descending loop of henle and enters the vasa recta. Solutes leave vasa recta.

50
Q

What is the countercurrent mechanism to increase vasa recta osmolality?

A

Solutes leave ascending loop of henle and enters the vasa recta while H2O leaves vasa recta.

51
Q

What are the 2 methods to regulate ECF osmolality? (i.e. loss in water OR solute)

A

ADH/vasopressin or thirst

52
Q

Where is ADH secreted from and stored in?

A

Secreted by the hypothalamus, stored in the posterior pituitary gland

53
Q

What stimulates ADH production?

A

High plasma osmolality or low plasma volume/blood pressure

54
Q

What is the effect of ADH binding to V1?

A

Causes vasoconstriction in vascular smooth muscles

55
Q

What is the effect of ADH binding to V2?

A

Increased water reabsorption and urine concentration via deposition of aquaporin channels on cell membranes

56
Q

What is SIADH

A

Too much ADH production!

57
Q

What is diabetes inspidus?

A

Failure to produce ADH/inability of kidney to respond to ADH –> inability to concentrate urine

58
Q

What is diabetes melitus?

A

Presence of glucose in urine, signaling malfunction of the kidney

59
Q

What is the way to regulate ECF volume (i.e. loss in water AND solute)

A

Activation of the renin-angiotensin-aldosterone axis

60
Q

What is the function of renin?

A

Activates angiotensin II

61
Q

Where is renin produced by?

A

Granular cells in the juxtaglomerular complex

62
Q

What stimulates the production of renin?

A

Increased sympathetic activity

63
Q

What is the function of angiotensin II?

A

Vasoconsctriction of efferent arterioles
Stimulates aldosterone secretion

64
Q

What is the function of aldosterone?

A

Increases Na+ reabsorption and K+ secretion via the Na+ K+ ATPase pump

Directly increases Na+ permeability by insertion of ENAC (NA+ channels)

65
Q

What stimulates aldosterone secretion?

A

Angiotensin II or increased extracellular K+ concentration

66
Q

Where does aldosterone function

A

Distal tubule

67
Q

What happens to the internal, external sphincter and detrusor muscles during bladder filling?

A

IS & ES contracted to maintain continence
Detrusor relaxed

68
Q

What happens to the internal, external sphincter and detrusor muscles during bladder emptying?

A

Detrusor contracts
ES contraction overrode by brain
IS relaxes for urination

69
Q

Process of acid regulation

A

H+ secreted, Na+ reabsorbed
H+ binds with HCO3- to form H2CO3
H2CO3 –> H2O + CO2 by carbonic anhydrase
H2O & CO2 diffuse into the tubular cells and H2CO3 reforms
Breakdown to H+ and HCO3-; H+ secreted and again

70
Q

What is the ratio of H+ secretion to Na, HCO3- reabsorption?

A

For everyone H+ secreted, 1 Na+ and 1 HCO3- is reabsorbed

71
Q

What is the compensatory mechanism for metabolic alkalosis?

A

Respiratory compensation to decrease ventilation = decreased CO2 excretion = higher pCO2

72
Q

What is the cause of metabolic alkalosis

A

Loss of H+ via vomiting/antacid ingestion

73
Q

What is the cause of respiratory alkalosis?

A

Hyperventilation = low pCO2 = low H+ production

74
Q

What is the compensatory mechanism for respiratory alkalosis?

A

Renal compensation to decrease H+ secretion and HCO3- reabsorption to increase arterial pH

75
Q

What is the cause of metabolic acidosis

A

Low H+ excretion/high H+ production/loss of HCO3- (diarrhoea)

76
Q

What is the compensatory mechanism for metabolic acidosis?

A

Respiratory compensation to increase ventilation (higher CO2 excretion = lower pCO2!)

77
Q

What is the cause of respiratory acidosis?

A

Decreased ventilation = high pCO2 = high H+ production

78
Q

What is the compensatory mechanism for respiratory acidosis?

A

Renal compensation to increase H+ secretion and HCO3- reabsorption to decrease arterial pH

LSM3214 (5 decks)

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