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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

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23
Q

Describe the structure of the podocyte layer

A

Contain pseudopodia which interdigitate and form filtration slits

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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
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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
  • PGC – Hydrostatic pressure in the capillary - biggest pressure from capillaries
  • PBC – Hydrostatic pressure in the Bowman’s capsule
  • πGC – Oncotic pressure (formed from proteins pulling water towards it) 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 Afferent Arteriole

II. Constrict Efferent Arteriole

  • this causes blood to be backed up in the glomerulus and increases the pressure of the blood in the capillary
  • Decrease GFR (Decrease PGC):

I. Dilate Efferent Arteriole

II. Constrict Afferent Arteriole

  • this backs up blood before the glomerulus so reduces the pressure of the blood in the glomerulus
37
Q

Describe the myogenic autoregulation of the BP

A
  • ↑ BP → afferent arteriole constriction (reduced blood in the glomerulus and build up of pressure before the glomerulus)
  • ↓ BP → afferent arteriole dilatation (more blood enters the glomerulus and therefore increases the pressure inside the glomerulus)

GFR is unchanged in both

38
Q

What does the tubuloglomerular feedback do?

A

TG feedback links Na and Cl conc at the macula densawith the control of renal arteriolar resistance

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

54
Q

name the three layers that make up the lining for the glomerulus

A
  • endothelial cells - thin, have pores to allow plasma to cross wall (not blood cells or platelets)
  • basement membrane -continuous layer of connective tissue and glycoproteins and prevents large molecules from being filtered
  • epithelial lining - podocytes let final filtration occur
55
Q

what does glomerular filtrate usually contain

A
  • no blood
  • no platelets
  • no protein
  • mainly organic solutes with a low molecular weight
  • inorganic ions
56
Q

define blood hydrostatic pressure

A
  • force from the capillaries, pushing contents out into the interstitial space
57
Q

define blood osmotic pressure

A
  • pressure if contents moving into the capillary from the interstitial fluid
58
Q

equation for net filtration

A

hydrostatic pressure in capillary - (hydrostatic pressure in Bowmans capsule + oncotic pressure difference the capillary and tubular lumen)

59
Q

what is acute tubular necrosis

A
  • damage to the cells of the kidney
  • There is a low pressure of blood in the capillaries
  • can cause ischemia and permanent damage
60
Q

Tubuloglomerular feedback mechanism for High BP

A
  1. high BP = more vol of blood so more vol of Na and Cl collects in the Macula Densa cells
  2. osmolality of the cell increases (water follows Na)
  3. water collects in the macula densa and cell expands
  4. swelling of the cells results in the release of ATP
  5. ATP - converted into adenosine inside the glomerulus
  6. adenosine binds to an A1 receptor on afferent arteriole
  7. Results in the vasoconstriction of the afferent arterioles
  8. reduces GFR and renin synthesis inhibited
61
Q

Tubuloglomerular feedback mechanism for low BP

A
  1. release prostaglandins (cause vasodilation)
  2. Renin is released
  3. RAAS system activated
  4. constriction of efferent arterioles
  5. increase GFR
62
Q

3 stimuli responsible for renin release

A
  1. sympathetic nervous system
  2. reduced stretch of the afferent arteriole
  3. signals in the macula densa cells in response to NaCl delivery

SA urinary (25 decks)

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