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Renal Exam 1 > Renal blood flow/glomerular filtration > Flashcards

Renal blood flow/glomerular filtration Flashcards

1
Q

Components of a nephron?

A
  • Glomerulus

- Tubule

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2
Q

Components of a nephron

-Glomerulus (glomerular capillaries) function?

A

Filters blood

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3
Q

Components of a nephron

-Tubule function?

A

Converts filtrate into urine

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4
Q

Components of a nephron

-Both the glomerulus and the tubule are surrounded by?

A

Both the glomerulus and the tubule are surrounded by the blind end of the tubular epithelium…bowman’s capsule (glomerular capsule)

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5
Q

The space between the capsule and the glomerulus is known as?
-What happens in this space?

A

-Bowman’s space-filtrate passes from blood to tubular system through this space

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6
Q

2 types of nephrons?

A
  • Cortical

- Juxtamedullary

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7
Q

Cortical nephrons

A
  • Short loops of Henle

- Surrounded by peritubular capillaries

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8
Q

Juxtamedullary nephrons

A
  • Long loops of Henle
  • Long efferent arterioles which divide into specialized peritubular capillaries called the vasa recta
  • Functions to concentrate urine
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9
Q

Renal blood flow

-Oxygen consumption of renal tissue is higher than that of brain-Why?

A

Related to high rate of active Na+ reabsorption (drives Na+/K+ ATPase)

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10
Q

Renal blood flow

-Blood flow to cortex compared to medulla?

A

Cortex receives more blood

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11
Q

Where does the renal medulla get its blood from?

A

the vasa recta

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12
Q

RBF determined by?

A

RBF is determined by pressure gradient between renal artery and renal vein divided by the vascular resistance

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13
Q

Glomerular filtration: first step in urine formation

A
  • Plasma is filtered under pressure from glomerular capillaries into Bowman’s capsule
  • Normally, glomerular filtrate is essentially free of blood cells and proteins but otherwise identical to plasma
  • Glomerular filtrate is heavily modified as it passes down the nephron
  • Urine is very different from glomerular filtrate
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14
Q

Clinical application

  • Estimation of GFR is essential in assessment of renal function
    • Total GFR?
A

Total GFR is the sum of the filtration rate in all functioning nephrons and therefore is an index of functioning renal mass

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15
Q

Clinical application

  • GFR estimate can be used to evaluate the severity and course of renal disease
    • A decrease in GFR indicates? Most often resulting from?
A

Disease progression most often resulting from a decrease in net permeability due to loss of filtration surface area
-Increase in GFR indicates at least partial recovery

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16
Q

Glomerular membrane: a molecular sieve

  • Passage of water and small solutes? Concentrations on each side of the membrane?
  • Passage of large molecules (proteins) and formed elements?
A
  • Free passage of water, small solutes (glucose, aas, electrolytes):concentrations are the same on both sides of the membrane
  • Passage of large molecules (proteins) and formed elements is impeded
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17
Q

How much protein is filtered into Bowman’s capsule under normal conditions?

A

Only very small amounts of proteins are filtered into Bowman’s capsule

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18
Q

Structure of glomerular membrane

  • Three distinct layers
    • Inner layer?
    • Middle layer?
    • Outer layer?
A
  • Inner layer-Fenestrated capillary endothelium
  • Middle layer-Glomerular basement membrane
  • Outer layer-Podocyte epithelium
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19
Q

Structure of glomerular membrane

  • Three distinct layers
    • Fenestrated capillary endothelium-highly permeable to?
A

Highly permeable to water and dissolved solutes

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20
Q

Structure of glomerular membrane

  • Three distinct layers
    • Glomerular basement membrane
A

Collagen, proteoglycans contain anionic (negative) charges

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21
Q

Structure of glomerular membrane

  • Three distinct layers
    • Podocyte epithelium-Function of the slit pores?
A

Slit pores between podocytes restrict large molecules

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22
Q

Slide 15 picture?

A

?

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23
Q

Mechanism of filtration

-Based on?

A

Based on size and charge of molecules

  • Larger molecules more restricted than smaller
  • Anionic molecules are restricted more than neutral or cationic
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24
Q

Graph on slide 17

A

?

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25
Q

Clinical application

  • Some kidney diseases cause loss of negative charge on the basement membrane before noticeable changes in renal structure
    • Called?
    • Results in?
A
  • Minimal change disease or nephropathy
  • Results in filtration of proteins (especially albumin) and their appearance in urine (proteinuria)
  • More extensive renal injury often results in large amount of protein in urine
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26
Q

Physical forces affecting glomerular filtration

-GFR is a product of 3 physical factors?

A
  • Hydraulic conductivity (Lp) of glomerular membrane (permeability of capillary wall)
  • Surface area for filtration
  • Capillary ultrafiltration pressure (Puf)
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27
Q

What is the product of the hydraulic conductivity and the surface area for filtration?

A

Ultrafiltration coefficient Kf

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28
Q

How can the ultrafiltration pressure be used to calculate GFR?

A

GFR = Kf x Puf

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29
Q

Normal GFR

  • in ml/min?
  • L/day?
A
  • 125 ml/min

- 180 L/day

30
Q

Mechanisms for altering GFR

-Altered Kf?

A

Mesangial cell concentration

31
Q

Mechanisms for altering GFR

-Altered Puf?

A

Changes in Pgc

32
Q

Pgc (pressure in glomerular capillaries?)

-Determined by 3 factors?

A
  • Renal arterial blood pressure
  • Afferent arteriolar resistance
  • Efferent arteriolar resistance
33
Q

Glomerular mesangial cells can alter Kf

-Contraction of mesangial cells has what effects?

A

Shortens capillary loops, lowers Kf, and thus lowers GFR

34
Q

Puf is determined by?

A

Hydrostatic and colloid osmotic pressures in glomerular capillaries

35
Q

Puf difference of three pressures?

A

slide 24?

36
Q

Glomerular filtration

-Depends on?

A

Depends on NET filtration pressure

Slide 25

37
Q

Glomerular and peritubular capillary starling forces

A

slide 26?

38
Q

Control of GFR by adjusting resistance of afferent and efferent arterioles
-Afferent arteriolar constriction

A
  • Greater pressure drop upstream of glomerular capillaries
  • Pgc decreases, which decreases GFR
  • Renal blood flow decreases due to increased resistance
39
Q

Control of GFR by adjusting resistance of afferent and efferent arterioles
-Efferent arteriolar constriction

A
  • Pooling of blood in glomerular capillaries
  • Increased Pgc increases GFR
  • Renal blood flow decreases
40
Q

The ‘garden hose’ analogy

A

Review this analogy as it makes it very easy to understand

41
Q

Probably should know the graphs on slide 33 and 35

A

?

42
Q

Renal blood flow

-Regulated by?

A
  • Regulated by several mechanisms in order to control GFR
  • Vascular resistance to RBF is primarily determined by afferent and efferent arterioles
  • Controlled by sympathetic nervous system (NE) and various hormones along with internal (myogenic, T-G feedback) control mechanisms
43
Q

Renal blood flow

-Autoregulation?

A

Process that regulates GFR over a MAP range between 80 and 170 mmHg

44
Q

Effects of sympathetic stimulation

A
  • Constriction of afferent and to a lesser extent, efferent arterioles
    • Decreased RBF and GFR
    • Diverts the renal fraction to vital organs
  • Increased renin secretion by granular cells
45
Q

Effects of sympathetic stimulation

  • Increased renin secretion by granular cells
    • Leads to production of? What are its effects?
A
  • Angiotensin II is produced-restores BP (systemic vasoconstriction)
  • Angiotensin II promotes arteriolar constriction (efferent > afferent), raises BP, and stabilizes GFR (moderate ang II)
  • Stimulates Na reabsorption in proximal tubule, thick ascending limb of Henle’s loop, DCT, CD
46
Q

Effect of renal prostaglandins?

-Release of prostaglandins enhanced by?

A
  • Renal prostaglandins dampen vasoconstriction by ang II and symp. activity
  • Release of prostaglandins enhanced by ADH
47
Q

Control of GFR and RBF-Effects of hormones/autacoids

-Effect on GFR by NE, Epi, and endothelin?

A

Decrease GFR

48
Q

-Effect on GFR by ang II?

A

No change (prevents decrease)

49
Q

-Effect on GFR by NO and prostaglandins?

A

Increase GFR

50
Q

Effect of changes in Starling forces on GFR and RBF

-Vasodilate afferent arteriole? Examples?

A

Increase RBF and GFR

Examples-prostaglandins E2/I2, bradykinin, NO, dopamine, ANP

51
Q

Effect of changes in Starling forces on GFR

-Vasodilate efferent arteriole? Examples?

A

Decreases GFR

Examples-ACE inhibitors, ARBs

52
Q

Effect of changes in Starling forces on GFR and RBF

-Constriction of afferent arteriole? What would do this?

A

Decrease RBF and GFR

Sympathetics

53
Q

Effect of changes in Starling forces on GFR and RBF

-Constriction of efferent arteriole? What would do this?

A

Maintain or increase GFR

Ang II

54
Q

Autoregulation

  • The kidney guards filtration carefully
  • This is accomplished by the glomerulus being situated between 2 arteriolar beds. Vascular tone in these 2 beds?
A
  • Protects the delicate glomerular architecture at times of high blood pressure
  • Preserves GFR at times of low systemic BP
55
Q

Autoregulation of RBF and GFR

A

-Process whereby RBF and GFR are maintained constant regardless of marked changes in BP by adjustments of afferent and efferent arteriolar resistance

56
Q

Autoregulation of RBF and GFR

-Effective range of control?

A

Effective range of control is between approximately 75-160 mmHg

57
Q

Autoregulation of RBF and GFR

-What would happen without autoregulation?

A

Without autoregulation, a small increase in BP would result in large increases in fluid excretion and volume depletion

58
Q

Mechanisms for autoregulating RBF and GFR

-Myogenic responses to?

A

Increased systemic arterial pressure

59
Q

Mechanisms for autoregulating RBF and GFR

-Tubuloglomerular feedback responses to?

A

Increased or decreased GFR

60
Q

Myogenic mechanism of autoregulation

A
  • Resistance of blood vessels to stretch when exposed to high arterial pressure
  • Via contraction of vascular smooth muscle in response to stretch with increased movement of Ca into cells
  • Prevents increases in RBF and GFR when BP increases
61
Q

Tubuloglomerular feedback

A
  • Autoregulation of GFR by the rate of fluid NaCl delivery to the macula densa
  • Feeds back to the kidneys to control renal afferent and efferent arteriolar resistance
62
Q

Tubuloglomerular feedback

-This process is regulated by the?

A

Juxtaglomerular apparatus which consists of the macula densa cells in the distal tubule and the juxtaglomerular cells in the walls of the afferent and efferent arterioles

63
Q

Tubuloglomerular feedback

-Process?

A
  • The macula densa cells sense NaCl concentration in the distal tubule
  • Feeds this information back to JG cells to adjust arteriolar resistance
  • Ensures constant delivery of Na to distal tubule and prevents changes in renal excretion
  • Renin release is also regulated here
64
Q

3 components of the juxtaglomerular apparatus?

A
  • Macula densa
  • Extraglomerular mesangial cells (lacis cells)
  • Juxtaglomerular (granular) cells in afferent and efferent arteriole smooth muscle
65
Q

Juxtaglomerular apparatus

-macula densa

A

in wall at beginning of DCT

66
Q

Juxtaglomerular apparatus

-how does it respond to changes in BP?

A

Maintains GFR nearly constant

67
Q

Tubuloglomerular feedback response to increased renal perfusion pressure?

A

Results in constriction of afferent arteriole with a decrease in GFR

68
Q

Vasoconstriction in response to tubuloglomerular feedback is mediated by?

A

Adenosine

69
Q

Tubuloglomerular feedback response to decreased renal perfusion pressure?

A

Flow chart on slide 51!

70
Q

Tubuloglomerular feedback response to decreased renal perfusion pressure
-Local responses which may be mediated via NO will cause?

A

afferent arteriolar dilation

71
Q

A couple clinical applications at the end you should probably review

A

…

72
Q

Renal functional unit= nephron

-What happens to the number of nephrons as a person ages?

A

The number of nephrons decreases with age

Renal Exam 1 (6 decks)

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