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Z MD1 Renal block > Physiology > Flashcards

Physiology Flashcards

(107 cards)

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0
Q

what is uremia

A

the accumulation of dozens of toxic metabolites (not only urea)

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1
Q

main functions of the kidneys (7)

A
  • water and sodium homeostasis
  • acid/base balance
  • control of ECF Ion conc
  • excretion of waste products and xenobiotics
  • endocrine functions
  • formation of concentrated urine
  • formation of dilute urine
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2
Q

which hormones do the kidneys make

A

EPO
renin
Vitamin D3
PGI2

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3
Q

what is the difference between superficial cortical glomeruli and juxtamedullary glomeruli

A

SCG - LOP penetrates only a short distance into the medulla and their efferent arterioles give rise to cortical capillaries surrounding the PCT and DCTs
JMG - LOP penetrates deep into the medulla and their efferent arterioles become the vasa recta that also penetrate deep into the medulla parallel to the LOH

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4
Q

what is the proportion between SCG and JMG?

A

JMG only make up 10% of glomeruli

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5
Q

main function of JMG

A

give the greatest responsibility to concentrating the urine - increase the osmolarity of the urine

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6
Q

what are the two parts of the proximal tubule

A

pars recta and PCT

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7
Q

what is the difference in the thin and thick parts of the ascending limb of the LOH between SCG and JMG?

A

SCG - thin is very short

JMG - thin is very long

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8
Q

how many nephrons do we have

A

2 million (1 million in each kidney)

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9
Q

what is the filtration fraction at the kidney

A

20% of the renal plasma flow

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10
Q

what is the GFR?

A

125ml/min

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11
Q

what is the volume of fluid that is passed through the kidneys a day

A

180L

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12
Q

at what point do you start to get problems if your GFR starts to drop

A

when it drops down to 30-40ml/min

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13
Q

where are the macula densa cells

A

epithelial cells of the thick ascending that lie against the afferent and efferent arterioles

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14
Q

what are the 2 components of renal autoregulation

A

myogenic response

tubuloglomerular reflex

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15
Q

what what range of MAP can the nephron keep the pressure constant in the glomerulus

A

70-180mmHg

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16
Q

How do macula densa cells participate in renal autoregulation

A

sense the NaCl that is delivered to it (if pressure too high, NaCl will be higher) –> releases adenosine and thromboxane to constrict the afferenent arteriole

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17
Q

what is the pressure in the glomeruli kept at

A

50mmHg

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18
Q

where are the cells that make renin?

A

they are the granular cells lining the afferent arteriole

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19
Q

three parts of the filtration complex of the glomerulus

A

fenestrations
basal lamina
slits between foot processes of podocytes

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20
Q

what stops most proteins moving through the glomerulus

A

their negative charge is repelled by the negative charge on the basal lamina and fenestrations

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21
Q

why in diabetes, does the amount of albumin increase in the urine

A

because in the diabetes the negative charge of the basal lamina is lost and so a disproportionate amount of albumin is allowed through the glomerulus and lost in the urine

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22
Q

what are the normal values of the forces acting towards filtration at the glomerulus

A

hydrostatic pressure in the glomerular capillary = 50mmHg
hydrostatic pressure in the bowmans capsule = 10mmHg
Oncotic pressure in the glomerular capillary = 25-40mmHg
oncotic pressure in the Bowmans capsule = 0mmHg

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23
Q

what is the net filtration pressure at the glomerules

A

10-15mmHg

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24
what happens to GFR when the afferent arteriole is constricted? What about the efferent arteriole?
afferent - GFR decreases due to decreased hydrostatic pressure efferent - GFR increases due to increased hydrostatic pressure
25
where does angiotensin 2 act in the kidney primarily
primarily on the efferent arteriole - constricts them (supporting filtration)
26
Ang2 inhibitors and their effect on the kidney
dilation of the efferent arteriole - decreases GFR
27
what is the equation for renal blood flow
change in pressure from renal artery to capillary / resistance of the afferent and efferent arterioles
28
what is the myogenic response
afferent arteriole constricts in response to stretch by increased pressure
29
three things that can cause renin release
- sympathetic activation - decreased BP in afferent arteriole - decreased NaCl delivery at the macula densa
30
what is the equation for renal clearance of a substance
urine volume x urine concentration / conc in blood
31
the clearance of substance x is equal to
the volume of plasma cleared of X per time
32
how much of the creatinine we produce is cleared
all of it
33
explain the renal clearance of penicillin
clearance is greater that filtration as extra is secreted into the urine
34
where is potassium, Ca and phosphate reabsorbed
primarily PT | DT to some extent
35
what controls the absorption of Ca
PTH and vitamin D3
36
how is phosphate absorbed
cotransported across with Na
37
which solvent is excreted completely
urea
38
which solvent is completely reabsorbed
glucose
39
how much water and salt is reabsorbed
water - 99% | Na - 99.5%
40
what is the osmolarity of the filtrate at the beginning of the nephron
~300mOsM
41
what is the max osmolarity that urine can get to
1200mOsM
42
what is absorbed in the descending LOH
water
43
what is absorbed in the thin ascending LOH
favours movement of NaCL into the ECF (passive reabsorption through PARACELLULAR junctions)
44
how is the filtrate in the lumen of the nephron dilute by the time it gets to the DT
because more Na is reabsorbed compared to water by this point
45
what causes the movement of water out of the descending LOH
urea conc in the ECF | Na conc in the ECF from the ascending LOH
46
what is the osmolarity of the urine by the end of the LOH
100mOsM
47
what is the range of osmolarity of the urine at the end of the collecting duct
50-1200mOsM
48
how is the amount of water reabsorbed regulated
by insertion of aquaporins in the CD
49
what is the mainstay cellular transport mechanism in the nephron?
3Na/2K ATPase on basolateral membrane
50
how is Na reabsorbed in the PT
by active transport by Na/K ATPase
51
what channels are on the apical membrane of the PT
Na cotransporter | Na/H+ exchanger
52
what types of substances does the Na cotransporter cotransport
glucose amino acids phsophate
53
how is Cl- ions absorbed in the PT
the movement of Na absorption leaves a negative charge in the lumen and therefore anions move along gradient through paracellular spaces and transcellularly
54
how does HCO3- get absorbed
due to Na/HCO3 transporter in the PT on the basolateral membrane. Gradient set up by Na/H+ exchanger on apical membrane moves TRANSCELLULARLY
55
how is water reabsorbed in the PT
moves by osmosis following gradient both paracellularly and transcellularly
56
what is solvent drag
the gradient that pulls water across the cells of the PT also pulls other things that are dissolved in it (K+, Ca+, )
57
between Cl and HCO3 which is preferentially reabsorbed in the early PT and what does this cause
HCO3 - causes conc of Cl to rise and by the late PT we have high Cl --> causes Cl reabsorption in the late PT paracellularly
58
what does the movement of Cl in the late PT lead to...
change in electrochemical gradient (now +3mV in lumen) --> Na reabsorption both paracellularly and transcellularly
59
what is absorbed in the thin LOH and how
Na by passive diffusion through tight junctions of paracellular pathway. No water
60
what is absorbed in the thick LOH and how
Na - by active reabsorption. No water
61
what is the transporter on the thick LOH apical membrane
Na/K/2Cl cotransporter
62
which drug inhibits the Na/K/Cl cotransporter
frusemide
63
what is the transporter on the DCT on the apical side
Na/Cl
64
which drug inhibits the Na/Cl transporter in the DCT
thiazide diuretics
65
which channels are on the apical side of the CD
K and Na channels (not active) | aquaporins if present
66
what is the definition of acute renal failure
urine flow less than 500ml/day
67
what is the definition of chronic renal failure
glomerular flow <72L/day | - typically occurring over a long time
68
how can you get glomerular disease and tubular disease of acute renal failure
can have just a loss of GFR with only minor impairment of tubular function, or can have minor loss of GFR with great impairment of tubular function
69
what are the endocrine sequalae that occurs with chronic renal failure
- excessive activation of RAS --> vasoconstriction - vitamin D activation - erythropoeitin decreases --> anaemia
70
why is plasma urea a poor guide to GFR
very variable in reabsorption (diet dependent)
71
what is the normal plasma clearance of creatinine
50-120microM/L
72
formula for working out creatinine clearance and therefore GFR
UV/P
73
how does a drop in systemic pressure to the kidneys result in acute renal failure
drops below 70mmHg --> kidney autoregulation fails --> decreased GFR --> anoxia and stasis --> formation of casts and death of tubular cells --> necrosis
74
what conditions are associated with anuria
``` ARF heroin overdose HSV2 prostatic malignancy mechanical obstruction drugs ```
75
pre-renal causes of ARF
``` shock sepsis haemolysis rhabdomyolysis nephrotoxic drugs ```
76
how does rhabdomylosis cause ARF
breakdown of skeletal muscle releases myoglobin --> toxic to the nephron --> necrosis
77
what are the causes of intrinsic ARF
glomerular disease interstitial nephris tubular damage
78
what do you have to be careful about in a patient with ARF
acidosis and hyperkalaemia
79
most common cause of post renal ARF
prostatic malignancy
80
what happens to the nephrons in chronic renal failure
remaining nephrons hypertrophy and are able to undergo hyperfiltration to try and compensate for the loss of the damaged nephrons
81
why is glomerula hypertrophy and hyperfiltration a bad thing during chronic renal failure
- because the tubules are not able to keep up with the filtrate and therefore the filtrate is not modified in the way it should be - causes glomerular hypertension --> further damage
82
presentation of a patient with chronic renal failure
``` fatigue loss of appetite skin pigmentation dehydration itchiness bleeding ```
83
what will the dipstick show in someone with CRF
specific gravity will be close to plasma (1.010)
84
common causes of CRF
diabetes hypertension chronic glomerulonephritis cystic disease
85
what are the consequences in salt and water imbalances with CRF predominately glomerular or predominantly tubular
glomerular - sodium retention and hypertension | tubular - sodium loss and low BP, impaired conc ability
86
why does acidosis occur during renal failure
due to the loss of tubular function - ammonia production by the kidney fails and you are not able to excrete H ions at the normal rate
87
what happens to the levels of Ca and PO4 during renal failure
rise in PO4 (due to reduced excretion) | reduction in Ca
88
why do you get bone disease with chronic renal failure
due to loss of Vit D3 and high PTH
89
normal value of HCO3
24mmol/L
90
normal value for pCO2
40mmHg
91
what can cause challenges to pH
pCO2, metabolism, gastrointestinal secretions, renal function
92
what acids are created in the body
- sulphuric and phsophoric acids from proteins and lipids - lactic acid anaerobic metabolism - keto acids from FAs
93
what would cause metabolic acidosis
chronic renal failure chronic diarrhoea (loss of bicarbonate) starvation
94
what can high levels of HCO3 mean
``` metabolic alkalosis respiratory acidosis (compensation) ```
95
what can low levels of HCO3 mean
``` metabolic acidosis respiratory alkalosis (compensation) ```
96
why does metabolic acidosis cause hyperkalemia
because the kidney swaps K for H when trying to excrete the excess H+ into the urine
97
how do you calculate the anion gap
(Na+ + K+) - (HCO3 + Cl-)
98
normal anion gap
12mmol/L
99
what is the major contributor to the anion gap
albumin
100
what conditions give acidosis with a high anion gap
lactic acidosis diabetic ketoacidosis renal failure
101
what happens as a result of alkalosis in regards to ion transport
type 2 intercalated cell: - excretion of HCO3 via antitransportation with Cl- in type 2 intercalated cell - H+ reabsorbed through antiporter with K+ and through its own ATP pump PCT - decreased HCO3 reabsorption in PCT (cotransporter with Na) - decreased H+ excretion (cotransporter with Na)
102
match up acidosis, alkalosis, hypokalaemia and hyperkalaemia
``` acidosis = hyperkalaemia alkalosis = hypokalaemia ```
103
what is the most important thing in defining renal failure
level of glomerular filtration rate
104
what can cause anuria
outlet obstruction eg. prostatic malignancy | renal artery occlusion
105
explain the water and Na problems that arise from chronic renal failure of predominantly glomerular basis and tubular basis
glomerular - Na retention and HT | tubular - Na wasting and low BP
106
response to acidosis
Type A intercalated cell - H+ pumped into the lumen by exchange of K+ and by own ATPase transporter -HCO3 pumped into interstitium by exchange of Cl PCT - excretion of NH4+ through glutamine excretion - excretion of phosphate

Z MD1 Renal block (8 decks)

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