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Renal Physiology Flashcards

1
Q

what are the 6 major functions of the kidney?

A

1) regulation of water and electrolyte balance
2) excretion of metabolic waste products/foreign chemicals
3) regulation of blood pressure
4) secretion of erythropoietin
5) secretion of 1,25-dihydroxyvitamin D3
6) regulation of extracellular pH

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2
Q

What are the kidneys?

A

2 retroperitoneal organs about the size of a fist (wt = 150g)

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3
Q

what is a nephron?

A

filtering units of the kidney each containing a selective filtering unit (glomerulus)

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4
Q

what percentage of volume is reabsorbed in the kidneys?

A

99%

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5
Q

what is urethritis?

A

inflammation of urethra

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6
Q

what is cystitis?

A

inflammation of bladder

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7
Q

what is pyelonephritis?

A

infection of kidney

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8
Q

what is the glomerulus?

A

highly specialized membrane for selective filtration, containing a network of capillaries between an afferent and efferent arteriole

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9
Q

what allows effective filtration at glomerulus?

A

large surface area that allows fluids and small molecules across but not protein

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10
Q

what is glomerular filtration rate? what is the normal range?

A

total movement of fluid across the glomerular membrane for all nephrons
100-125mL/min

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11
Q

What is the flow of blood through the glomerulus?

A 
afferent arteriole
glomerular capillaries (filtration site)
efferent arteriole
peritubular capillars and vasa recta
venules
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12
Q

where are the two capillary beds (glomerulus and peritubular) located in relation to one another?

A

two capillar beds in parallel

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13
Q

where is bowman’s capsule?

A

surrounding glomerulus

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14
Q

what are the 3 layer of the glomerular membrane?

A 
endothelial cells
basement membrane (basal lamina)
podocytes (foot processes)
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15
Q

describe the endothelial cells

A

perforated and have pores

contain fenestrations

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16
Q

describe the basal lamina

A

acellular

contains collagen and glycoprotein

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17
Q

describe podocytes

A

epithelial cells that encircle glomerular tuft

there are narrow slits between podocytes

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18
Q

what is the glomerular membrane sensitive to?

A

changes in BP and P sub GC

changes in Glc levels

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19
Q

what are the 3 glomerular cell types?

A

mesangial cells
macula densa
juxtaglomerular apparatus

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20
Q

what are the mesangial cells?

A

muscle cells between capillary loops that are able to contract and decrease GFR

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21
Q

what are the mesangial cells?

A

muscle cells between capillary loops that are able to contract and decrease GFR

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22
Q

where is the macula densa? what is its function?

A

located in early distal tubule and between afferent/efferent arterioles
detects changes in tubular fluid

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23
Q

what is the function of the JGA?

A

contain granule cells that secrete renin and other vasoactive chemicals

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24
Q

how are the JGA and macula densa related?

A

macula densa can detect changes in tubular fluid and tell JGA to release agents to regulate GFR accordingly (through vasoconstriction/dilation)

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25
what drives filtration?
starling forces
26
what is P sub GC?
pressure in glomerular capillary | acts on bowman's capsule
27
what is pi sub BC?
oncotic pressure of filtrate in Bowman's capsule
28
what is P sub BC?
pressure in bowman's capsule | acts on glomerulus
29
what is pi sub GC?
oncotic pressure of plasma in glomerular capillary
30
what is Kf?
filtration coefficient (leakiness)
31
what 2 forces favour filtration?
P sub GC | pi sub BC
32
what 2 forces oppose filtration?
P sub BC | pi sub GC
33
what is the main determinant of GFR? what happens if you increase or decrease it?
P sub GC incr: GFR increases (leads to damage of glomerular membrane) decr: GFR decreases
34
what controls P sub GC?
afferent and efferent arterioles
35
what controls P sub GC? what hormones are involved?
afferent and efferent arterioles | ang 2 and NE
36
what happens to PsubGC if you constrict afferent arteriole? efferent arteriole?
``` aff = decr PsubGC eff = incr PsubGC ```
37
what happens to PsubGC if you constrict afferent arteriole? efferent arteriole?
``` aff = decr PsubGC eff = incr PsubGC ```
38
what are two intrarenal mechanisms and what is their overall function?
1) myogenic (generated within muscle) 2) tubuloglomerular feedback keep RBF (renal blood flow) and GFR constant of wide range of BP
39
how does myogenic mechanism keep RBF and GFR constant?
prevents increase in PsubGC and GFR by constricting the muscle when theres increased BP
40
how does tubuloglomerular feedback help keep RBF and GFR constant?
tubules talk to glomerulus macula densa detects changes in fluid flow/content in distal tubule and tells JGA to release constrictor/dilator accordingly
41
how does tubuloglomerular feedback help keep RBF and GFR constant?
tubules talk to glomerulus macula densa detects changes in fluid flow/content in distal tubule and tells JGA to release constrictor/dilator accordingly
42
what does the myogenic and tubular glomerular feedback mechanisms do when there is an increase in RBF?
protect PsubGC myogenic contstricts afferent tubular glomerular feedback reduces flow to prevent PsubGC from going up
43
what does the myogenic and tubular glomerular feedback mechanisms do when there is an increase in RBF?
protect PsubGC myogenic contstricts afferent tubular glomerular feedback reduces flow to prevent PsubGC from going up
44
what 3 substances are released when there is volume depletion/low BP? what causes each release?
baroreceptor reflex incr NE decr renal perfusion incr ang 2 decr BP incr ADH
45
use of NE, Ang 2 and ADH may cause severe vasoconstriction. what do the kidneys do to prevent that?
release of vasodilatory prostaglandins
46
use of NE, Ang 2 and ADH may cause severe vasoconstriction. what do the kidneys do to prevent that?
release of vasodilatory prostaglandins
47
how are prostaglandins formed?
membrane phospholipids are converted to arachidonic acid cyclooxygenase, COX1 and COX2 convert arachidonic acid to prostaglandin intermediates which go on to become prostaglandins
48
how are prostaglandins formed?
membrane phospholipids are converted to arachidonic acid cyclooxygenase, COX1 and COX2 convert arachidonic acid to prostaglandin intermediates which go on to become prostaglandins
49
how could aspirin cause renal failure?
prostaglandins prevent intence constriction of afferent/efferent caused by Ang 2 and NE aspirin can block prostaglandin and allow severe constrition
50
what is creatinine?
natural product of muscle metabolism and constant from day to day and freely filtered (not secreted or reabsorbed) estimates GFR
51
what are 3 values to know the importance of?
1) creatinine clearance 2) MDRD eGFR equation to estimate GFR 3) blood urea/creatinine ratio to determine volume depletion
52
what is the problem with eGFR?
only accurate with patients who have GFR less than 60 and have been stable for a period of time
53
what can blood urea:creatinine ratio tell us?
early volume depletion | if over 0.07, then hypovolemia
54
what is the relationship between plasma creatinine and GFR? why is this significant?
``` inverse relationship (filtration goes down, plasma Cr goes up) a small change in plasma Cr may reflect a large change in GFR ```
55
what is the relationship between plasma creatinine and GFR? why is this significant?
``` inverse relationship (filtration goes down, plasma Cr goes up) a small change in plasma Cr may reflect a large change in GFR ```
56
how much is reabsorbed in the proximal tubule?
95%
57
what does the negatively charged barrier of the glomerulus do
repel proteins, making the filtrate protein free
58
what is reabsorbed at proximal tubule?
water/Na (55-70%) HCO3 (85%) Glucose (100%) small amount of filtered protein (95%)
59
what does volume depletion do to proximal tubule? How?
increases reabsorption since there is a decre in water and solute increases constriction of afferent and efferent (dec. RBF but efferent constriction corrects drop in PsubGC) decreases plasma osmotic pressure in peritubular capillaries
60
what can volume depletion do to drug/metabolites?
increase reabsorption which can be toxic
61
what is different about the blood going to peritubular capillaries when there is volume depletion?
increased protein conc and increased osmolality
62
what does less blood flow mean in terms of RBF?
greater fraction of RBF is filtered and protein is left behind in blood
63
what is the equation for excretion?
exc = filtration - reabsorption + secretion | when reabsorption is 100%, then filtration = reabsorption
64
what happens to excretion, reabsorption, filtration with increase plasma Glc?
filtration goes up excretion does not go up until there is quite a big incr in plasma glc (transport maximum = Tm) reabsoprtion goes up until certain point (Tm) is reached
65
what happens to excretion, reabsorption, filtration with increase plasma Glc?
filtration goes up excretion does not go up until there is quite a big incr in plasma glc (transport maximum = Tm) reabsoprtion goes up until certain point (Tm) is reached
66
what is the function of descending loop of henle?
reabsorbs water | increases concentration of electrolytes in filtrate
67
what 2 conditions are required to pull water out from lumen of descending tubule?
high water permeability so water can freely pass but not ions hypertonic interstitum causing osmotic forces to pull water from lumen
68
what is the function of the ascending loop of henle?
Na, Ca, Cl, Mg, and Ca are reabsorbed | Water is left behind (dilutes)
69
what is the function of the distal tubule?
Na and Ca (PTH activated) reabsorption | water left behind (dilutes)
70
what is the function of collecting ducts?
Na reabsorbed, K secreted (as a loss) water reabsorbed if ADH present H+ excreted concentrates urine
71
what parts of the nephron segments are in the adrenal medulla? cortex?
cortex: distal tubule, proximal tubule and part of collecting duct medulla: loop of henle, part of collecting duct
72
what causes renin release?
decreased RA pressure, decr Na load, decr renal perfusion pressure, beta-adrenergic receptor stimulation
73
what is the function of ang 2?
``` vasoconstrictor release aldosterone increase thirst increase Na appetite increase ADH increase NE release ```
74
what happens when BP decreases?
baroreceptors increase Sym nerve activity (incr HR and contractility) renin release leads to ang 2 formation, leading to aldosterone release and Na retention
75
how does converting enzyme affect bradykinin?
causes it to be inactive, leading to decreased vasodilation and increased TPR
76
how does converting enzyme affect bradykinin?
causes it to be inactive, leading to decreased vasodilation and increased TPR
77
what increases aldosterone?
ang 2 potassium ACTH
78
what does aldosterone do?
incr Na reabsorption but incr K loss | incr H loss
79
what does ADH do?
opens water channels (incr water reabsorption in collecting ducts) vasoconstriction thirst
80
what causes ADH release?
incr in osmolality of plasma | decr blood volume
81
what two receptors activate ADH?
osmoreceptors | baroreceptors
82
what two receptors activate ADH?
osmoreceptors | baroreceptors
83
what is the major prostaglandin in the kidney? what triggers PG production?
PGE2 | NE and ang 2
84
what are 3 sources of calcium?
GI tract kidneys bone
85
how much caclium is reabsorbed in kidneys and where is it reabsorbed the most?
99% 60% proximal tubule (distal tubule under PTH control)
86
what does PTH do in GI?
stimulates activation of vit D to increase interstinal Ca absorption
87
what does PTH do in kidneys?
incr calcium reabsorption in distal tubule and decr phosphate reabsorption in proxminal tubule
88
what does PTH do in bone?
mobilizes Ca from bone to ECF
89
what does Vit D do in GI?
incr Ca and phosphate absorption in gut
90
what does Vit D do in bone?
incr responsiveness of bone to PTH to incr Ca mobilization
91
what does Calcitonin do?
works primarily in bone to decr Ca movement from bone fluid to plasma and decr bone resoprtion (inhibits osteoclasts)
92
what does erythropoietin do?
increases hemoglobulin synthesis and production of RBCs when there is hypoxia

Medical Physiology (15 decks)

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