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renal physiology Flashcards

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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
What is the plasma osmolality at the end of the descending limb
1200mosm
26
What is permeable at the descending limb
Water is the only permeable thing
27
What is permeable at the ascending limb
Only solutes Water is impermeable here
28
What is the counter-current exchanger
Vasa recta
29
Where is glucose reabsorbed
100% is reabsorbed at the proximal convoluting tubule
30
90% of what is reabsored at the proximal convoluted tubule
Bicarbonate
31
Sodium is reabsored at 65% where ?
Proximal convoluted tubule this also means 65% of water is also reabsored
32
What is 100% reabsorbed at the proximal convoluting tubule
Glucose Amino acids Lactate
33
Is phosphate excreted or reabsorbed at the p.c.t ?
Excreted due to inhibition of transporter via binding of PTH
34
How do the other ions ie Cl, Ca, Mg, K get reabsorbed ?
Via Paracellular transport via tight junctions About 50-55% reabsorbed
35
How are lipids reabsorbed into the blood ie urea
They can pass through the phospholipid bilayer - passive diffusion
36
what makes up the renal corpuscle ?
Glomerulus and bowman’s
37
What makes up bowman’s
Podocytes
38
What makes up glomerulus
Glom. Basement membrane. + endothelial lining
39
What charge is the GBM and why is this relevant to filtration
Negative charge on the GBM repels negatively charged particles ie plasma proteins (albumin IgG) Acts as a filter in this way
40
What particles are attracted to the GBM
Na+ K+ (Positively charged -> attracted to negatively charged GBM) So these particles will pass through the glomerular capsule
41
What’s gets through the GBM ?
Positively charged molecules of < 7.9nm (Bicarbonate, glucose, insulin, haemoglobin, amino acids, creatinine, vitamins, sodium/potassium/chloride/magnesium)
42
What happens is macro-molecules manage to pass through the renal corpuscle ?
Mesangial cells phagocytose them
43
What do molecules have to pass through to make it into the proximal convoluted tubule ?
(In order) Fenestrated capillaries GBM Filtration slit Podocytes and nephrin
44
What is nephrin
A protein that sits in between Podocytes that allows only really small particles through (7-9nm)
45
What is the filtration slit
Space between nephrin proteins and GBM
46
What is the glomerular filtration rate ?
How much viscous plasma is passing through the glomerular to Bowman’s capsule every minute
47
What is the average GFR
125ml/min
48
What influences GFR
Permeability NFR (net filtration pressure) And surface area (of glomerulus)
49
What are the pressures (NFR) acting on GFR
- glomerular hydrostatic - Colloid osmotic - capsular hydrostatic pressure (All these together = NFR = 10mmHg into Bowman’s)
50
What is glomerular hydrostatic pressure
Affected by blood pressure Pushes things OUT of capillaries into Bowmans At about 55mmHg
51
What is osmotic colloid pressure ?
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
What is capsular hydrostatic pressure ?
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
Why does decreased surface area decrease GFR ?
54
What is KF
The filtration co-efficient GFR = NFR + KF
55
What stimulates the secretion of potassium / K+
Aldosterone - otherwise all K+ would be reabsorbed via proximal and distal convoluted tubule
56
What is arterial natriuretic peptide
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
What does ANP do ?
Promotes excretion of sodium and diuresis
58
What does PTH do ?
Increases calcium reabsorption Decrease phosphate reabsorption
59
Which nephron structure is especially important in the kidneys ability to produce urine of varying concentration
Loop of henle
60
What is the GFR
A protein free plasma Is formed as a result of passive forces acting across the glomerular membrane
61
When arterial BP is elevated above normal - what is a compensatory charge in renal function
Afferent arteriolar vasodilation
62
What is the renal threshold
Plasma concentration of a particular substance at which its Tm is reached and the substance first appears in the urine
63
Function of aldosterone
Stimulates sodium reabsorption in the distal and collecting tubules Stimulates potassium secretion in the distal tubule
64
Where does water absorption occur to the greatest extent
Proximal convoluted tubule
65
Where is water reabsorption under the control of vasopressin
Distal and collecting tubules
66
What is plasma clearance
Volume of plasma that is completely cleared of a substance by the kidney in one minute of time
67
What establishes the medullary vertical osmotic gradient by means of counter-current multiplication
Loops of henle of juxtamedullary nephrons
68
Action of vasopressin
Activates cyclic AMP second-messenger system within the tubular cells
69
Nephrotoxic drugs
NSAIDs Aminoglycosides ACEi ARBs Diuretics
70
How to remove potassium from the body ?
Calcium resonium Loop diuretics Dialysis
71
What is oliguria
Urine output of less than 0.5ml/kg/hr
72
How to detect AKI
Urine output - oliguria Fluid overload Rise in potassium, urea, creatinine (normally excreted out)
73
KDIGO definitions on detecting AKI
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
Diagnosis of AKI ?
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
EGFR for kidney failure
Less than 15
76
*urine has brown granular casts
Acute tubular necrosis
77
Mechanism of action of spironolactone
Aldosterone antagonist
78
Common causative organism for post-strep. Glomerulonephritis in young kids
Strept. Pyogenes
79
*crescentic glomerulonephritis
GPA
80
What is renal papillary necrosis
Coagulative necrosis of renal papillae due to: Pyleonephritis Diabetic nephropathy Analgesic nephropathy Sickle cell anaemia
81
How does renal papillary necrosis present ?
Visible haematuria Loin pain Proteinuria History of migraines
82
*tram-track appearance
Membranoproliferative glomerulonephritis (type 1)
83
*loss of subcutaneous tissue from patient face?
Type 2 membranoproliferative glomerulonephritis
84
What type of cells line distal convoluted tubule
Simple cuboidal cells These allow for reabsorption via sodium-chloride co-transporter Also found in thick ascending limb of the loop of Henle
85
Effect of alkalosis on potassium
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
What is the main osmotically active ion in the intracellular compartment
Potassium
87
Which cells sit between the glomerular capillary loops and binds them together
Mesangial cells
88
What is the specific component of the GBM that makes it negatively charged - and so able to repel plasma proteins of similar charge?
Heparin sulfate
89
What is the most accurate measure(r) of eGFR
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
Is the N/L/2Cl co-transporter found in the thick or thin ascending loop of henle
Thick
91
side effect of metformin
Compensated metabolic acidosis (lactic acidosis)
92
What is the active form of vitamin D
Calcitriol
93
What converts 25,hydroxyvitamin D3 into calcitriol
1-alpha-hydroxylase (in the kidney)
94
Function of calcitriol
Binds to vitamin D receptor for a variety of functions , including bone health , calcium regulation and immune function
95
Where are aqua-porin-2 channels
Distal convoluted tubule and collecting tubules (AV1 = descending loop of Henle)
96
Dysfunction of the proximal convoluted tubule results in what type of renal tubular acidosis ?
Proximal RTA type 2
97
Causes of RTA type II
Carbonic anhydride inhibitors ie acetazolamide

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