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renal physiology Flashcards

1
Q

What is the medullary interstitium

A

Space between nephrons and medulla of the kidney

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2
Q

What makes the medullary interstitium more concentrated

A

Sodium chloride urea

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3
Q

Which cells in the juxtoglomerular apparatus are responsible for sensing the conc. of sodium chloride in the distal convoluted tubule

A

Macula densa cells

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4
Q

What cells release renin

A

Granular cells (juxtoglomerular)

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5
Q

What cells make up the juxtoglomerular apparatus

A

Extraglomerular mesangial cells
Granular cells
Macula densa cells

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6
Q

How to differentiate between central diabetes insipidus and nephrogenis DI

A

Water deprivation test

Central = ADH deficiency
Nephrogenic = reduced ADH detection in the kidney

Urine osmolality will increase on administration of desmopressin in central DI but not in nephrogenic

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7
Q

What causes release of ADH

A

Increased plasma osmolality

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8
Q

what two structures make up the renal corpuscle

A

Bowman’s capsule + glomerulus

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9
Q

Which component of the nephron is responsible for reabsorption of sodium

A

Proximal convoluted tubule

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10
Q

why is creatinine a good measurement of GFR

A

It is freely filtered at the glomerulus and not reabsorbed

Therefore creatinine clearance rate is reflective of hoe well the kidney is working

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11
Q

How does renin-angiotensin correct a dehydrated state

A

Renin-angiotensin system stimulated
Sodium ion uptake in the distal convoluted tubule increased

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12
Q

Which ion provides the concentration gradient for the absorption of solutes ?

A

Sodium

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13
Q

What is the countercurrent system

A
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14
Q

What is the typical value of GFR in a healthy 20 year old

A

90-120mL/min

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15
Q

What helps differentiate between pre-renal AKI and acute tubular necrosis

A

Fractional excretion of sodium

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16
Q

*renal biopsy shows subepithelial immunoglobulin and complement deposits on the glomerular basement membrane , basement membrane is also thickened

A

Membranous nephropathy

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17
Q

Management of anti-GBM/ good pastures

A

High dose corticosteroids, cyclophosphamide and plasmapheresis

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18
Q

Treatment of HUS

A

Supportive with fluid rehydration
Haemofiltration
Steroids
Plasmapheresis

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19
Q

What is contained within the nephron

A

Glomerulus
Bowmans
Proximal con. Tubule
Descending l.o.h
Ascending ll.o.h
Distal convoluted. Tubule

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20
Q

Where are aquaporin 1 channels found

A

Descending loop

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21
Q

Features of aquaporin 1

A

These are always open in the descending limb

Allows for passive loss of water

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22
Q

What is the counter-current multiplier mechanism

A

Describes Na/K/2Cl co-transporter pumping solutes into the medullary interstitium and as a result the passive diffusion of water into the medullary interstitium via aquaporin channels

This mechanisms allows for the slow removal of sodium and chloride

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23
Q

What is the plasma osmolality at bowman’s and proximal convoluted tubule

A

300mosm

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24
Q

What’s is the plasma osmolality at the distal convoluted tubule / end of ascending limb

A

325 mosm

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25
Q

What is the plasma osmolality at the end of the descending limb

A

1200mosm

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26
Q

What is permeable at the descending limb

A

Water is the only permeable thing

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27
Q

What is permeable at the ascending limb

A

Only solutes

Water is impermeable here

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28
Q

What is the counter-current exchanger

A

Vasa recta

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29
Q

Where is glucose reabsorbed

A

100% is reabsorbed at the proximal convoluting tubule

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30
Q

90% of what is reabsored at the proximal convoluted tubule

A

Bicarbonate

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31
Q

Sodium is reabsored at 65% where ?

A

Proximal convoluted tubule this also means 65% of water is also reabsored

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32
Q

What is 100% reabsorbed at the proximal convoluting tubule

A

Glucose
Amino acids
Lactate

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33
Q

Is phosphate excreted or reabsorbed at the p.c.t ?

A

Excreted due to inhibition of transporter via binding of PTH

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34
Q

How do the other ions ie Cl, Ca, Mg, K get reabsorbed ?

A

Via Paracellular transport via tight junctions

About 50-55% reabsorbed

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35
Q

How are lipids reabsorbed into the blood ie urea

A

They can pass through the phospholipid bilayer - passive diffusion

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36
Q

what makes up the renal corpuscle ?

A

Glomerulus and bowman’s

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37
Q

What makes up bowman’s

A

Podocytes

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38
Q

What makes up glomerulus

A

Glom. Basement membrane. + endothelial lining

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39
Q

What charge is the GBM and why is this relevant to filtration

A

Negative charge on the GBM repels negatively charged particles ie plasma proteins (albumin IgG)

Acts as a filter in this way

40
Q

What particles are attracted to the GBM

A

Na+
K+

(Positively charged -> attracted to negatively charged GBM)

So these particles will pass through the glomerular capsule

41
Q

What’s gets through the GBM ?

A

Positively charged molecules of < 7.9nm

(Bicarbonate, glucose, insulin, haemoglobin, amino acids, creatinine, vitamins, sodium/potassium/chloride/magnesium)

42
Q

What happens is macro-molecules manage to pass through the renal corpuscle ?

A

Mesangial cells phagocytose them

43
Q

What do molecules have to pass through to make it into the proximal convoluted tubule ?

A

(In order)

Fenestrated capillaries
GBM
Filtration slit
Podocytes and nephrin

44
Q

What is nephrin

A

A protein that sits in between Podocytes that allows only really small particles through (7-9nm)

45
Q

What is the filtration slit

A

Space between nephrin proteins and GBM

46
Q

What is the glomerular filtration rate ?

A

How much viscous plasma is passing through the glomerular to Bowman’s capsule every minute

47
Q

What is the average GFR

A

125ml/min

48
Q

What influences GFR

A

Permeability
NFR (net filtration pressure)
And surface area (of glomerulus)

49
Q

What are the pressures (NFR) acting on GFR

A
  • glomerular hydrostatic
  • Colloid osmotic
  • capsular hydrostatic pressure
    (All these together = NFR = 10mmHg into Bowman’s)
50
Q

What is glomerular hydrostatic pressure

A

Affected by blood pressure
Pushes things OUT of capillaries into Bowmans

At about 55mmHg

51
Q

What is osmotic colloid pressure ?

A

Affected by proteins in blood ie myeloma increases proteins

This pressure tries to keep water in arterioles - so exerts a pressure of 30mmHg against Bowman’s capsule

Action is exerted by albumin

52
Q

What is capsular hydrostatic pressure ?

A

Affected by calculi stuck in the nephron

This pressure is a back flow pressure , created when molecules pass from Bowmans -> prox. C.t. This creates a back pressure on capillary bed

Ie a car at 0mph has no air resistance but a car at 60mp will have air resistance (back pressure)

This pressure is about 15mmHg (acting against Bowmans)

53
Q

Why does decreased surface area decrease GFR ?

A
54
Q

What is KF

A

The filtration co-efficient

GFR = NFR + KF

55
Q

What stimulates the secretion of potassium / K+

A

Aldosterone - otherwise all K+ would be reabsorbed via proximal and distal convoluted tubule

56
Q

What is arterial natriuretic peptide

A

Produced by the heart and stored in atrial muscle cells

Released when the atrial cells are mechanically stretched due to an increase in the circulating plasma volume

57
Q

What does ANP do ?

A

Promotes excretion of sodium and diuresis

58
Q

What does PTH do ?

A

Increases calcium reabsorption

Decrease phosphate reabsorption

59
Q

Which nephron structure is especially important in the kidneys ability to produce urine of varying concentration

A

Loop of henle

60
Q

What is the GFR

A

A protein free plasma
Is formed as a result of passive forces acting across the glomerular membrane

61
Q

When arterial BP is elevated above normal - what is a compensatory charge in renal function

A

Afferent arteriolar vasodilation

62
Q

What is the renal threshold

A

Plasma concentration of a particular substance at which its Tm is reached and the substance first appears in the urine

63
Q

Function of aldosterone

A

Stimulates sodium reabsorption in the distal and collecting tubules

Stimulates potassium secretion in the distal tubule

64
Q

Where does water absorption occur to the greatest extent

A

Proximal convoluted tubule

65
Q

Where is water reabsorption under the control of vasopressin

A

Distal and collecting tubules

66
Q

What is plasma clearance

A

Volume of plasma that is completely cleared of a substance by the kidney in one minute of time

67
Q

What establishes the medullary vertical osmotic gradient by means of counter-current multiplication

A

Loops of henle of juxtamedullary nephrons

68
Q

Action of vasopressin

A

Activates cyclic AMP second-messenger system within the tubular cells

69
Q

Nephrotoxic drugs

A

NSAIDs
Aminoglycosides
ACEi
ARBs
Diuretics

70
Q

How to remove potassium from the body ?

A

Calcium resonium

Loop diuretics

Dialysis

71
Q

What is oliguria

A

Urine output of less than 0.5ml/kg/hr

72
Q

How to detect AKI

A

Urine output - oliguria
Fluid overload
Rise in potassium, urea, creatinine (normally excreted out)

73
Q

KDIGO definitions on detecting AKI

A
  1. Rise in serum creatinine of 26 micro mol/litre or greater within 48 hours
  2. 50% rise in creatinine known or presumed to have occurred within past 7 days
  3. Call in UO to less than 0.5ml/kg/hr for more than 6 hours in adults
74
Q

Diagnosis of AKI ?

A

All patient with suspected AKI need urinalysis done , also if there is no identifiable cause or at risk of UTI then do a renal USS within 24 hours of assessment

75
Q

EGFR for kidney failure

A

Less than 15

76
Q

*urine has brown granular casts

A

Acute tubular necrosis

77
Q

Mechanism of action of spironolactone

A

Aldosterone antagonist

78
Q

Common causative organism for post-strep. Glomerulonephritis in young kids

A

Strept. Pyogenes

79
Q

*crescentic glomerulonephritis

A

GPA

80
Q

What is renal papillary necrosis

A

Coagulative necrosis of renal papillae due to:

Pyleonephritis
Diabetic nephropathy
Analgesic nephropathy
Sickle cell anaemia

81
Q

How does renal papillary necrosis present ?

A

Visible haematuria
Loin pain
Proteinuria

History of migraines

82
Q

*tram-track appearance

A

Membranoproliferative glomerulonephritis (type 1)

83
Q

*loss of subcutaneous tissue from patient face?

A

Type 2 membranoproliferative glomerulonephritis

84
Q

What type of cells line distal convoluted tubule

A

Simple cuboidal cells

These allow for reabsorption via sodium-chloride co-transporter

Also found in thick ascending limb of the loop of Henle

85
Q

Effect of alkalosis on potassium

A

A metabolic alkalosis causes the stimulation of beta-intercalated cells to re-absorb hydrogen ions in the kidney collecting ducts

Some hydrogen is re absorbed into co-transport with potassium —> therefore intracellular H+ and K+ within the intercalated cells will increase

This create a K+ concentration gradient that promotes passive transport of potassium from intercalated beta cells into tubule

This results in increased potassium excretion and therefore a transient hypokalaemia

86
Q

What is the main osmotically active ion in the intracellular compartment

A

Potassium

87
Q

Which cells sit between the glomerular capillary loops and binds them together

A

Mesangial cells

88
Q

What is the specific component of the GBM that makes it negatively charged - and so able to repel plasma proteins of similar charge?

A

Heparin sulfate

89
Q

What is the most accurate measure(r) of eGFR

A

Inulin

(It is freely filtered at the glomerulus and is not reabsorbed or secreted in the kidney tubules)

A decline in GFR = incline in inulin

90
Q

Is the N/L/2Cl co-transporter found in the thick or thin ascending loop of henle

A

Thick

91
Q

side effect of metformin

A

Compensated metabolic acidosis (lactic acidosis)

92
Q

What is the active form of vitamin D

A

Calcitriol

93
Q

What converts 25,hydroxyvitamin D3 into calcitriol

A

1-alpha-hydroxylase (in the kidney)

94
Q

Function of calcitriol

A

Binds to vitamin D receptor for a variety of functions , including bone health , calcium regulation and immune function

95
Q

Where are aqua-porin-2 channels

A

Distal convoluted tubule and collecting tubules (AV1 = descending loop of Henle)

96
Q

Dysfunction of the proximal convoluted tubule results in what type of renal tubular acidosis ?

A

Proximal RTA type 2

97
Q

Causes of RTA type II

A

Carbonic anhydride inhibitors ie acetazolamide

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