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(LUSUMA) Urinary System > S3) GFR and Glomerulus > Flashcards

S3) GFR and Glomerulus Flashcards

1
Q

Label the following blood vessels showing the blood supply and drainage of the kidney:

A
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2
Q

Label the following structures in the lobe of the kidney:

A
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3
Q

Describe the anatomical course of blood supply from the aorta to the peritubular capillaries / vasa recta

A

Abdominal aorta → renal artery → segmental artery → interlobar artery → arcuate artery → interlobular artery → afferent arteriole → glomerulus → efferent arteriole → peritubular capillaries / vasa recta

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4
Q

Describe the anatomical course of blood drainage from the interlobular vein to the inferior vena cava

A

Interlobular vein → arcuate vein → interlobar vein → segmental vein → renal vein → inferior vena cava

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5
Q

Where do the peritubular capillaries drain?

A

Peritubular capillaries drain into the interlobular veins

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6
Q

Where do the vasa recta drain into?

A

Vasa recta drain into interlobular veins and arcuate veins

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7
Q

Compare and contrast the cortical and juxtamedullary nephrons in terms of:

  • Location
  • Glomerulus size
  • Loop of Henle
A
  • Cortical nephron:

I. Found in outer part of cortex

II. Small glomerulus

III. Short LoH slightly in medulla

  • Juxtamedullary nephron:

I. Found in inner part of cortex next to medulla

II. Big glomerulus

III. Long LoH in medulla

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8
Q

Compare and contrast the cortical and juxtamedullary nephrons in terms of:

  • Diameter of afferent arteriole
  • Course of efferent arteriole
A
  • Cortical nephron:

I. AA diameter > EA diameter

II. EA forms peritubular capillaries

  • Juxtamedullary nephron:

I. AA diameter = EA diameter

II. EA forms vasa recta

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9
Q

Compare and contrast the cortical and juxtamedullary nephrons in terms of:

  • Sympathetic nerve stimulation
  • Concentration of renin
  • Ratio
A
  • Cortical nephron:

I. Rich stimulation

II. High [renin]

III. 90% in kidney

  • Juxtamedullary nephron:

I. Poor stimulation

II. Low [renin]

III. 10% in kidney

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10
Q

What is the value for renal blood flow?

A

Renal Blood Flow (RBF) is ~1.1L/min

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11
Q

How is renal plasma flow calculated?

A
  • Haematocrit is normally ~0.45
  • Hence, plasma ~ 0.55

Plasma x RBF = RPF

0.55 x 1.1L /min = 605 mL/min of plasma

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12
Q

Where is the glomerulus found?

A

In the cortex

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13
Q

What happens to the blood in the glomerulus?

A
  • 20% of blood from renal artery is filtered at any one time
  • 80% blood arriving exits via efferent arteriole (unfiltered)
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14
Q

What is the normal total glomerular filtrate per day?

A

140 – 180 L /day (~125 ml/min)

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15
Q

Which two structures compose the renal corpuscle?

A
  • Glomerulus
  • Bowman’s capsule
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16
Q

State the structure and function of the renal corpuscle

A
  • Structure: filtration barrier produced by capillary endothelium and visceral layer of Bowman’s capsule
  • Function: produces ultra filtrate of plasma
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17
Q

What sort of epithelium is found in the parietal layer of Bowman’s capsule?

A

Simple squamous epithelium

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18
Q

Filtration is a selective process.

Which substances are filtered and which aren’t?

A
  • Filtered: water, salts and small molecules
  • Not filtered: cells and large proteins
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19
Q

What is the end product of filtration?

A

The end product of filtration (ultrafiltrate) is identical to plasma without the large proteins and cells

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20
Q

Identify the 3 layers of the filtration barrier

A
  • Capillary endothelium
  • Basement membrane
  • Podocyte layer (visceral layer)
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21
Q

Describe the structure and function of the capillary endothelium

A
  • Structure: permeable
  • Function: filtrate (H2O, salts, glucose) moves between cells
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22
Q

Describe the structure and function of the basement membrane

A
  • Structure: acellular gelatinous layer of collagen/glycoproteins
  • Function:

I. Permeable to small proteins

II. Glycoproteins (- charge) repel protein movement

23
Q

Describe the structure of the podocyte layer

A

Contain pseudopodia which interdigitate and form filtration slits

24
Q

Explain the role of permeable selectivity of the filtration barrier to ensure the overall selectivity of filtration

A

Only particles with the following pass through:

  • Small molecular weight
  • Effective radius less < 1.48 nm
25
Q

Explain the effect of the filtration barrier’s charge on ensuring the overall selectivity of filtration

A
  • Negative charge of barrier repels proteins (only a few small proteins pass through)
  • Removing this negative charge increases the filtration of anions e.g. proteinuria
26
Q

Identify the three physical forces involved in the filtering of plasma to form ultra filtrate

A
  • P<strong>GC</strong> – Hydrostatic pressure in the capillary
  • P<strong>BC</strong> – Hydrostatic pressure in the Bowman’s capsule
  • π<strong>GC</strong> – Oncotic pressure difference between the capillary and tubular lumen
27
Q

What conditions are necessary for the net filtration pressure to decrease?

A
  • PGC decreases
  • PBC increases
  • πGC increases
28
Q

What conditions are necessary for the net filtration pressure to increase?

A
  • PGC ​increases
  • PBC decreases
  • πGC decreases
29
Q

Which pressure gradient favours filtration?

A

PGC – hydrostatic pressure in plasma

30
Q

Which pressure gradient opposes filtration?

A
  • PBC – hydrostatic pressure in tubule
  • πGC – oncotic pressure in glomerulus
31
Q

Identify three processes that drive the autoregulation of the glomerulus

A
  • Myogenic mechanism
  • Tubuloglomerular feedback
  • Glomerulotubular balance
32
Q

Why do we need the autoregulation of GFR?

A
  • Keeps RBF and GFR constant
  • Within the range 80-180 mmHg
33
Q

What would happen if we didn’t have autoregulation?

A

Slight change in BP would cause significant change in GFR:

E.g. 25% increase in BP → 125 mmHg → 225 L/day GFR → 4.6L day urine

34
Q

What does the myogenic mechanism entail?

A
  • Arterial smooth muscle responds to increases and decreases in vascular wall tension
  • Occurs rapidly
35
Q

The myogenic mechanism is a property predominantly of the preglomerular resistance vessels.

Identify them

A
  • Arcuate arteries
  • Interlobular arteries
  • Afferent arteriole
36
Q

Illustrate how the myogenic response is PGC regulated

A
  • Increase GFR (Increase PGC)

I. Dilate AA

II. Constrict EA

  • Decrease GFR (Decrease PGC):

I. Dilate EA

II. Constrict AA

37
Q

Describe the myogenic autoregulation of the BP

A
  • ↑ BP → afferent arteriole constriction
  • ↓ BP → afferent arteriole dilatation

GFR is unchanged in both

38
Q

What does the tubuloglomerular feedback do?

A

TG feedback links control of distal solute delivery to the JGA with renal arteriolar resistance and hence, tubular reabsorption

39
Q

What are the two components of TG feedback?

A
  • Afferent arteriole resistance
  • Efferent arteriolar feedback (hormonal)
40
Q

Explain how changes in tubular flow rate change the amount of NaCl that reaches the distal tubule

A

Increased aBP

= Increased PGC

= Increased RPF

= Increased GFR

= Increased [Na+] and [Cl+] in distal tubule

41
Q

What role do macula densa cells have in autoregulation?

A

Macula densa cells are sensors of DCT luminal [NaCl]

42
Q

The macula densa stimulates the juxtaglomerular apparatus to releases chemicals which regulate arterial tone.

Identify them and their effects

A
  • Adenosine: reduces GFR (A1 receptors constrict AA and A2 receptors dilate EA)
  • Prostaglandin: increases GFR (vasodilates AA)
43
Q

Sympathetic nerve fibres innervate AA and EA.

What effect does this have?

A
  • Sympathetic innervation is low (no effect on GFR)
  • Vasoconstriction can be stimulated by fight/flight, haemorrhage or ischaemia (reduces GFR)
44
Q

What effect does the parasympathetic nervous system have on the kidney?

A

PNS releases nitrous oxide for endothelial cells and vasodilation

45
Q

Autoregulation by glomerulotubular balance is a second line of defence.

What does it do?

A

Glomerulotubular balance blunts Na+ excretion response to any GFR changes

46
Q

What type of epithelia is found in the proximal convoluted tubule?

A

Simple cuboidal epithelia

47
Q

What adaptation do cells in the PCT have to help reabsorption?

A
  • Microvilli
  • Numerous mitochondria
48
Q

What type of epithelia is found in the descending limb of the Loop of Henle?

A

Simple squamous epithelia

49
Q

Why are there few mitchondria in the cells of the descending limb of the Loop of Henle?

A
  • Only passive transport occurs
  • ATP is not needed
50
Q

What type of epithelia is found in the ascending limb of the Loop of Henle?

A

Simple squamous epithelia

51
Q

Which organelle is abundant in the cells of the ascending limb of the Loop of Henle and why?

A
  • Mitochondria
  • Active absorption of Na+, K+, Cl-
52
Q

What type of epithelia is found in the collecting duct?

A
  • Simple columnar epithelium (no microvilli)
  • Simple cuboidal epithelium (no microvilli)
53
Q

What structure is formed from the merging of the collecting ducts and what does it do?

A

Papillary duct – acts as a gateway to the minor calyx

(LUSUMA) Urinary System (23 decks)

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