Lecture 29: The Nephrons Flashcards

1
Q

What is a nephron?

A

A microscopic functional unit of the kidney

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2
Q

Approximately how many nephrons are there per kidney?

A

1 million

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3
Q

What are nephrons responsible for the formation of?

A

Urine

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4
Q

What are the 2 types of nephrons?

A
  • Cortical nephrons

- Juxtamedullary nephrons

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5
Q

What % of nephrons are cortical nephrons?

A

85%

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6
Q

Where do cortical nephrons lie?

A

In the cortex

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7
Q

Where do Juxtamedullary nephrons extend?

A

Deep into the medulla

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8
Q

What are Juxtamedullary nephrons important for?

A

Formation of concentrated urine

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9
Q

What are the 3 functions of the nephron?

A
  • Selectively filter blood
  • Return to blood anything to be kept
  • Carry waste away for expulsion
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10
Q

What is each nephron comprised of?

5

A
  • Renal corpuscle
  • Proximal convoluted tubule
  • Nephron loop
  • Distal convoluted tubule
  • Collecting duct
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11
Q

What is each nephron associated with?

2

A
  • A glomerulus

- Peritubular capillaries

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12
Q

What are glomerular capillaries specialised for?

A

Filtration

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13
Q

What are glomerular capillaries?

A

Thin walled single layer of fenestrated endothelial cells

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14
Q

What are glomerular capillaries fed/drained by?

A

Arterioles

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15
Q

What is tightly regulated around glomerular capillaries?

A

Blood pressure

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16
Q

What are peritubular capillaries specialised for?

A

Absorption

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17
Q

What do peritubular capillaries wrap around?

A

Renal tubules

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18
Q

What do peritubular capillaries receive blood from/via?

A

From the glomerulus via efferent arterioles

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19
Q

What do the peritubular capillaries receive reabsorbed filtrate from?

A

Nephron

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20
Q

Some non-filtered solutes that need to be excreted can pass from the peritubular capillaries to where?

A

Into the nephron

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21
Q

What are vasa recta?

A

Extensions of pertibular capillaries that follow nephron loops deep into the medulla

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22
Q

Where are vasa recta found?

A

Only with juxtamedullary nephrons

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23
Q

What are renal corpuscles?

A

A glomerulus enclosed by the glomerular capsule

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24
Q

The renal corpuscle is where what meet?

A

The capillary and nephron

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25
Q

The renal corpuscle is the site of what?

A

The filtration barrier

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26
Q

What is the glomerular capsule?

A

The first part of the nephron

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27
Q

What 2 layers make the glomerular capsule?

A
  • Outer parietal layer

- Inner visceral layer

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28
Q

What is the parietal layer of the glomerular capsule made from?

A

Simple squamous cells

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29
Q

What is the visceral layer of the glomerular capsule made from?

A

Podocytes

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30
Q

What is between the outer parietal layer and the inner visceral layer of the glomerular capsule?

A

Capsular space

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31
Q

What does the capsular space receive?

A

Filtrate

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32
Q

What do podocytes surround?

A

The glomerular capillaries

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33
Q

Podocytes are very branched, very specialised what?

A

Epithelium

34
Q

Podocyte branches form intertwining what?

A

Foot processes called pedicels

35
Q

What forms between pedicels?

A

Filtration slits

36
Q

What happens to filtered blood going through filtration slits?

A

It passes into capsular space

37
Q

Where does the filtration barrier lie?

A

Between blood and capsular space

38
Q

What does the filtration barrier allow the free passage of?

A

Water and small molecules

39
Q

What does the filtration barrier restrict?

A

The passage of most proteins

40
Q

What is not filtered through the filtration barrier into the nephron?

A

Red blood cells

41
Q

What are the 3 layers of the filtration barrier?

A
  • Fenestrated endothelium of glomerular capillary
  • Fused basement membrane
  • Filtration slits between the pedicels of the podocytes
42
Q

Urine is waste fluid and what?

A

Solutes filtered from the blood

43
Q

Not everything that is filtered is what?

A

Excreted

44
Q

What happens to some filtrate?

A

It is reabsorbed

45
Q

Some of what isn’t filtered, is secreted where?

A

Into the nephron

46
Q

Urine = ?

A

Filtered - Reabsorbed + secreted

47
Q

What is the function of the proximal convoluted tubule?

A

Carry out the bulk of reabsorption

48
Q

What are proximal convoluted tubules surrounded by?

A

Peritubular capillaries

49
Q

What cells make up the proximal convoluted tubule?

A

Cuboidal epithelial cells

50
Q

There is a dense what on the luminal membrane of the proximal convoluted tubule?

A

Microvilli (brush border)

51
Q

The proximal convoluted tubule has a highly folded what?

A

Basolateral membrane

52
Q

The proximal convoluted tubule has many mitochondria for what?

A

Active transport

53
Q

Where does the nephron loop extend down into?

A

The medulla

54
Q

What is the length of the nephron loop important for?

A

Production of dilute/concentrated urine

55
Q

What is the nephron loop in juxtamedullary nephrons surrounded by?

A

Vasa recta

56
Q

What are the 4 regions of the nephron loop?

A
  • Thick descending limb
  • Thin descending limb
  • Thin ascending limb
  • Thick ascending limb
57
Q

What is the structure of the thick descending limb of the nephron loop?

A

Similar to PCT structure

58
Q

What is the structure of the thin descending limb of the nephron loop?

A

Simple squamous epithelium

59
Q

What is the structure of the thin ascending limb of the nephron loop?

A

Simple squamous epithelium

60
Q

What is the structure of the thick ascending limb of the nephron loop?

A

Similar to DCT structure

61
Q

The nephron loop has different permeabilities to what?

A

Water and sodium

62
Q

What is the function of the distal convoluted tubule?

A

Fine tuning/regulated absorption (hormonal regulation)

63
Q

What cells make up the distal convoluted tubule?

A

Cuboidal epithelium, but thinner than PCT

64
Q

Because there are only a few microvilli on the distal convoluted tubule there is no what?

A

Brush border

65
Q

there are fewer what at the distal convoluted tubule?

A

Mitochondria

66
Q

What is reabsorption mainly influenced by in the distal convoluted tubule?

A

Aldosterone

67
Q

What is the function of the collecting duct?

A

Fine tuning/regulated absorption

68
Q

Filtrate from several DCT’s drain into what?

A

One collecting duct

69
Q

What is the structure of collecting ducts?

A

Wall of simple cuboidal epithelium

70
Q

What 2 cells are found in Collecting duct walls?

A
  • Principal cells

- Intercalated cells

71
Q

What is the role of principle cells?

A

Reabsorption

72
Q

What is the role of intercalated disks?

A

Acid/base balance

73
Q

What is reabsorption in the collecting duct influenced by?

2

A
  • ADH

- Aldosterone

74
Q

What is the juxtaglomerular apparatus?

A

A specialised zone in every nephron

75
Q

Where is the juxtaglomerular apparatus located?

A

Where DCT lies against afferent arterioles

76
Q

What are the specialised cells of the DCT in the juxtaglomerular apparatus?

A

Macula densa cells

77
Q

What are the specialised cells of the afferent arterioles in the juxtaglomerular apparatus?

A

Juxtaglomerular cells

78
Q

What are macula densa cells?

A

Chemoreceptors detecting sodium levels

79
Q

What are Juxtaglomerular cells?

A

Mechanoreceptors that detect blood pressure

80
Q

What does the juxtaglomerular apparatus control?

A

The glomerular filtration rate

81
Q

What does the juxtaglomerular apparatus ensure?

A

The system is working at full capacity

82
Q

What does the juxtaglomerular apparatus stabilise?

A

Blood pressure