RENAL Renal blood flow and glomerular filtration Flashcards

1
Q

How much do kidneys weigh in males and females?

A

150g in male and 135g in female

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2
Q

How many nephrons are there in each kidney?

A

1 million nephrons in each kidney

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3
Q

What is the blood flow rate in the kidneys?

A

1.1L/min

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4
Q

What is part of the tubular structure of the nephron?

A
  1. Proximal convoluted tubule
  2. Loop of Henle
  3. Distal convoluted tubule
  4. Collecting ducts
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5
Q

What is the structure of the proximal convoluted tubule?

A

Cells with numerous mitochondria, apical tight junction and numerous microvilli

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6
Q

What type of cells does the descending loop of henle have?

A

Descending – thin permeable cells

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7
Q

What type of cells does the ascending loop of henle have?

A

Ascending - thick cells with numerous mitochondria

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8
Q

What cells is the juxtaglomerular apparatus made up of?

A

Macula Densa + Lascis cells + Granular cells of Afferent arteriole

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9
Q

What are the 2 types of cells in collecting duct?

A

-Principal cells
-Intercalated cells

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10
Q

What is the structure of principal cells and what are they responsible for?

A

tall, responsible for sodium absorption and vasopressin action

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11
Q

What is the structure of intercalated cells and what are they responsible for?

A

more microvilli, numerous mitochondrion and responsible for acid secretion

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12
Q

What is the size of the glomerulus in the corpuscle?

A

220 μm

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13
Q

What is the corpuscle?

A

Ball of capillaries supplied by afferent and efferent arterioles

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14
Q

What structure is the corpuscle surrounded by and what does this structure hold?

A

Surrounded by Bowmans capsule which holds filtered fluid (urine)

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15
Q

What is the total area of the corpuscle?

A

0.8m^2

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16
Q

What cells are found in the corpuscle?

A

Mesangial cells(pericytes)

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17
Q

What do mesangial cells reduce when they contract?

A

Contract to reduce glomerular volume

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18
Q

What do mesangial cells secrete?

A

Secretes extracellular matrix

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19
Q

What are the 3 layers in the glomeluar filtration barrier?

A
  1. Endothelium
  2. Basement membrane
  3. Podocytes
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20
Q

What is the size of endothelial fenestration?

A

70-90nm

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21
Q

What are podocytes also known as and what is there size?

A

-Filtration slit
-25nm

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22
Q

Up to what sized molecules does the glomerulus allow free movement?

A

Glomerulus allows free movement <4nm [7000
Da]

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23
Q

Above what sized molecule does the glomerulus stop free movement?

A

stops everything >8 nm [60,000 Da]

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24
Q

What rate of blood flow does the kidney receive?

A

Kidneys receive 1.1L/min

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25
Q

What % of the cardiac output do the kidneys receive

A

20% of cardiac output

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26
Q

What is the renal cortical blood flow rate?

A

5ml/g/min

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27
Q

What is the renal cortical arterio-venous oxygen difference and PO2?

A

14ml/L; pO2=50 mmHg

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28
Q

What is the renal medulla blood flow rate and PO2 ?

A

2.5ml/g/min pO2=15 mmHg

29
Q

What drives the fluid out to make filtrate in the glomerulus?

A

In the glomerulus the capillary hydrostatic
pressure drives the fluid out to make the filtrate

30
Q

What drives solutes into the descending vasa recta?

A

In the descending vasarecta the osmotic
pressure drives solutes in

31
Q

What vertebrae level is the sympathetic preganglionic supply for renal blood vessels from?

A

Sympathetic preganglionic is from T10-L2

32
Q

Where do the postganglionic neurons lie which supply renal blood vessels?

A

Postganglionic neurons lie in superior mesenteric and renal artery ganglion

33
Q

What are sympathetic fibers distributed through in the kidney?

A

Sympathetic fibres are distributed through the afferent arterial, efferent arterial
and juxtaglomerular apparatus

34
Q

What type of innovation happens at the loop of henle?

A

Noradrenergic innovation also happens at the loop of Henle

35
Q

What do nociceptive afferents run parallel to?

A

Nociceptive afferents run parallel to sympathetic fibres

36
Q

What is the renorenal-reflex in ureteric obstruction?

A

Ureteric obstruction –> Decrease efferent nerve stimulation –> Increase Na/Water excretion

37
Q

What is the effect of norepinephrine on renal blood flow?

A

Constriction

38
Q

What is the effect of dopamine on renal blood flow?

A

Dilation

39
Q

What is the effect of angiotensin 2 on renal blood flow?

A

Constriction

40
Q

What is the effect of prostaglandin 1 on renal blood flow?

A

Dilation

41
Q

What is the effect of acetylcholine on renal blood flow?

A

Dilation

42
Q

What is the effect of a high protein diet on renal blood flow?

A

Increase renal blood flow

43
Q

What is the effect of increasing renal nerve stimulation when norepinephrine acts on juxtaglomerular apparatus?

A

Increase in renin

44
Q

What is the effect of increasing renal nerve stimulation when norepinephrine acts on PCL, TALH, DCT ?

A

Increase in sodium absorption

45
Q

What is the effect of increasing renal nerve stimulation when norepinephrine acts on alpha 1 and alpha 2 receptors?

A

Reduce renal blood flow

46
Q

What does the glomerulus preserve during auto-regulation and what is this in response to?

A

The glomerulus can autoregulate its blood supply in response to systemic blood pressure changes to preserve the filtration pressure

47
Q

What are the steps involved in the renin angiotensin aldosterone axis?

A
  1. Renin released from juxtaglomerular apparatus converts angiotensinogen into angiotensin 1
  2. Angiotensin 1 converted into angiotensin 2 by ACE
  3. Angiotensin 2 acts on adrenal cortex which releases aldosterone.
  4. Aldosterone causes:
    -Decreased Na+(and water) excretion –> Increased extracellular fluid volume –> Increased renal arterial mean pressure, decreased discharge of renal nerves
48
Q

What may a sudden increase in blood pressure do to the glomerulus?

A

Sudden increases in blood pressure increases glomerular blood flow
and GFR potentially, may damage the glomerulus

49
Q

What prevents a sudden increase in blood pressure to glomerulus which could potentially increase GFR?

A

This is prevented by the “myogenic reflex”

50
Q

How does the myogenic reflex work when theres an increased blood pressure?

A

-There’s an increase in stretch
-This results in depolarisation
-This causes opening of voltage gated calcium channels causing an increasing in calcium
-Results in muscle contraction of the afferent artery to reduce blood flow

51
Q

What autoregulation happens to the GFR in response to increased flow in tubule, what is this orchestrated by and what is this feedback called?

A

-In response to increased flow in the tubule the GFR decreases
-This is orchestrated at the juxtaglomerular apparatus
-This is called ‘tubo-glomerular feedback

52
Q

What is the juxtaglomerular apparatus?

A

The JG apparatus is a special structure in the nephron at the junction of distal tubule with it own afferent artery

53
Q

How does the juxtaglomerular feedback work?

A

-Mechanism increased Na entry into macula densa cells
-Leads to more AYP breakdown
-This causes adenosine secretion which results in Calcium release
-Resulting in vasoconstriction of afferent artery

54
Q

What is renal blood flow calculated from?

A

Calculatef rom renal plasma flow and haematocrit

55
Q

What is used to measure renal plasma flow?

A

Renal plasma flow is measured using p-aminohippuric acid clearance

56
Q

What is the equation for renal blood flow?

A

Blood flow = Arterial concentration - venous concentration

57
Q

What can cause a decreased GFR?

A

-Constricted afferent artery
-Dilated efferent artery

58
Q

What can cause an increased GFR?

A

-Constricted efferent artery
-Dilated afferent artery

59
Q

What are the 2 targets in systemic hypotension that are autoregulated in kidneys?

A

-Afferent arteriolar vasodilation
-Efferent arteriolar vasoconstriction

60
Q

What is afferent arteriolar vasodilation mediated and prevented in what groups?

A

-Mediated by prostaglandin
-Prevented in old age, diabetes, NSAIDS

61
Q

What is efferent arteriolar vasconstriction mediated by and prevented by?

A

-Mediated by angiotensin II
-Prevented by ACEi, ARB

62
Q

What can prevention of afferent arteriolar vasodilation and efferent arteriolar vasoconstriction predispose and cause?

A

Prevention of afferent arteriolar vasodilatation and efferent arteriolar vasoconstriction predisposes and causes AKI

63
Q

What is the equation renal plasma flow?

A

Renal plasma flow = Upah x V/Arterial pah

64
Q

Why is venous PAH zero in measurement of renal plasma flow?

A

Venous PAH is zero as all of it is removed

65
Q

Why is it effective to use PAH as an effective way to measure effective renal plasma flow?

A

p-amino hippuric acid [PAH] and most (90%) of it removed in single passage through kidney, leaving nothing in renal vein;
and if it is not metabolized, stored, or produced by the kidney and does not itself affect blood flow

66
Q

What equation is used to estimate actual renal plasma flow?

A

Estimate actual renal plasma flow = [effective renal plasma flow]/0.9

67
Q

What equation is used to estimate renal blood flow?

A

Estimate renal blood flow = [actual renal plasma]/1-haematocrit

68
Q

What is the equation for clearance of a substance?

A

Clearance of a substance = Urine conc X urine flow