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3B week 1 - abnormal urine > renal physiology > Flashcards

renal physiology Flashcards

1
Q

what are the two capillary beds of the renal circulation

A
  1. glomerular
  2. peritubular
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2
Q

how are the renal capillary beds arranged and how are they separated

A

arranged in series, separated by the efferent arteriole -> helps to maintain pressure in both beds

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3
Q

what is the normal filtration rate of the kidney

A

180L/day

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4
Q

how much water is excreted via urine a day

A

1.5L

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5
Q

what is the solute conc in urine

A

600 miliosmoles

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6
Q

3 fundamental functions of the kidney

A
  1. filtration
  2. regulation (BP, electrolytes, Acid base etc.)
  3. production + activation of key hormones (erythrocytosis, etc.)
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7
Q

what are the 6 overarching effects the kidney has

A
  1. volume regualtion
  2. concentration
  3. pH
  4. metabolic
  5. excretory
  6. endocrine
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8
Q

how is volume regulated by the kidneys

A

directly through excretion/retention of fluid -> this results in BP control

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9
Q

what is the metabolic function of the kidney (2)

A
  1. gluconeogenesis -> usually immesuarable amounts but when fasting can produce a lot of glucose
  2. Vit D activation (CaPO4 metabolism)
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10
Q

endocrine functions of the kidney (3)

A
  1. RAAS -> produced renin
  2. EPO - erythrogenesis
  3. vit D control
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11
Q

why must blood flow be controlled in the renal system (2)

A
  1. blood flow is related to the function of the kidney (filtration + excretion) so must be maintained
  2. in order to protect the delicate arteries of the renal system -> autoregulation
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12
Q

what is the main purpose of blood flow in the kidney

A

to supply enough plasma to govern rate of filtration needed for bodily fluid volume and solute control

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13
Q

what is GFR determined by

A

net filtration pressure across the glomerular capillaries

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14
Q

what is glomerular blood flow directly proporitonal to

A

changes in pressure

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15
Q

what are the 2 major sites of resistance control in the kidney vascular bed

A

afferent and efferent ARTERIOLES

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16
Q

how is control of blood flow, hydrostatic pressure and filtration maintained by the arterioles

A

selective vasoconstriction and dilation of the afferent and efferent arterioles results in highly sensitive control of blood flow etc.

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17
Q

how does increased Afferent resistance change renal blood flow and net ultrafiltration pressure

A

RBF - decreased
NFP - decreased

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18
Q

how does decreased Afferent resistance change renal blood flow and net ultrafiltration pressure

A

RBF - increased
NFP - increased

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19
Q

how does increased Efferent resistance change renal blood flow and net ultrafiltration pressure

A

RBF - decreased
NFP - increased

20
Q

how does decreased Efferent resistance change renal blood flow and net ultrafiltration pressure

A

RBF - increased
NFP - decreased

21
Q

what are the key mediators for renal blood flow (6)

A

vasoconstrictors
1. sympathetic nerves
2. angiotensin II

vasodilators
3. prostoglandins
4. natriuretic peptides
5. nitric oxide
6. bradykinin

22
Q

how do sympathetic nerve influence renal blood flow

A
  1. release NA into the intersititial space in response to low fluid volume/fight or flight response
  2. high levels of NA causes vasoconstriciton of both afferent and efferent arterioles
  3. decrease in blood flow
  4. reduced fluid loss
23
Q

how does angiotensin II influence renal blood flow

A

causes vasoconstriction of the afferent and efferent arterioles in response to low extracellular volume

24
Q

what other mediator does angiotensin II work alongside

A

prostoglandins -> ultimately results in efferent constriction > afferent thus maintaining GFR when renal perfusion is reduced

25
Q

how do prostaglandins influence renal blood flow

A
  1. dampen the effect of vasocontrictors but causing dilation of the afferent arteriole
  2. cause vasodilation to prevent harmful vasoconstriciton and renal ischaemia
26
Q

how do natiuretic peptides influence renal blood flow

A

released from the heart in response to increased pressure and effective circulating volume -> causes vasodilation of the arterioles -> increased blood flow and GFR

ANP also inhibits the secretion of renin => less angiotensin II

27
Q

what are the 2 main natriuretic peptides

A

BNP; ANP

28
Q

what is the purpose of renal autoregulation

A

to maintain bloodflow and GFR within narrow limits despite changes in mean arterial pressure (changes between 60-100 mmHg)

29
Q

what are the 2 basic mechanism of renal autoregualtion

A
  1. myogenic response of smooth muscle of afferent arterioles
  2. tubuloglomerular feedback mechanism
30
Q

what is the myogenic response in renal autoregulaton

A

the inherent ability of the blood vessels to respond to changes in vessel circumference by constricting/relaxing
-> constriction in response to increased pressure prevents the vessel from being overstretched and also increases vascular resisitance to prevent excessive increase in renal blood flow and GFR when BP rises

venturi effect

31
Q

what is the bayliss effect

A

describes the reaction of smooth muscle cells in the arterial wall to changes in blood pressure

32
Q

how does the tubuloglomerular mechanism of renal autoregulation work (8)

A
  1. increased GFR
  2. flow through proximal tubule increases
  3. flow past macula densa increases
  4. in response to increased NaCl detection, the macula densa sens paracrine signals to the afferent arteriole
  5. afferent arteriole constricts
  6. resistance in afferent arteriole increases
  7. hydrostatic presure in glomerulus decreases
  8. GFR decreases
33
Q

what is the renal corpuscle made up of

A
  1. glomeralus
  2. bowman’s capsule
34
Q

are there arteries and veins in the renal corpuscle

A

no, only arterioles

35
Q

what is the glomerular filtrate

A

the blood that enters the glomerulus to be filtered via the ultrafiltration barrier

36
Q

above what size molecules are filtered out the capsules in ultrafiltration (i.e what size can pass through)

A

<1.8 nM

37
Q

what are the 3 layers of the ultrafiltration barrier and what do they allow to pass through

A
  1. fenstrated capillaries - allows anything except for blood cells to pass through
  2. basement membrane - prevents filtration of large proteins
  3. podocytes - part of the bowmans capsule, only allows small molecules to pass through
38
Q

apart from the filtration layers, how else is the ultarfiltration barrier molecule selective

A

it is charge selective -> the layers contain-vely charged glycoprotiens which makes it hard for polar molecules e.g. albumin to pass through even if they are within the size range

39
Q

what is hydrostatic pressure

A

the force exerted by a fluid on the walls of its comprtment

40
Q

what is oncotic pressure

A

the pressure exerted by plasma proteins (most notibly albumin) -> pulls water back into the capillary

41
Q

what forces oppose the hydrostatic pressure of the glomerular filtrate

A

the oncotic pressure of the filtrate (only minute as not many proteins in the glomerular filtrate) and the hydrostatic pressure of the bowman’s capsule

42
Q

what is the renal net filtration pressure equation

A

NFP = glomerular hydrostatic pressure - (bowmans capsule hydrostatic pressure + glomerular oncotic ressure)

43
Q

what is GFR

A

glomerular filtration rate - the total filtrate produced by ALL renal corpuscles in BOTH kidneys in 1 min

44
Q

what factors does the GFR take into account (3)

A
  1. NFP
  2. SA available for filtration
  3. prermeability of the glomerulus
45
Q

how can GFR change

A

change in filtration coefficent or NFP

46
Q

what is the MOA of ADH

A
  1. ADH release begins when plasma osmolarity is <280 mOS/L
  2. ADH acts on the distal convoluted tubule and collecting duct to increase water reabsorption independent of sodium
  3. ADH stimulates the insertion of aquaporin-2 channels onto the luminal membrane, allowing the free entry of water
  4. ADH also causes vasoconstriction of arterioles

-> water is retained

3B week 1 - abnormal urine (5 decks)

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