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HUBS192 2024 > Lecture 29: THE NEPHRON > Flashcards

Lecture 29: THE NEPHRON Flashcards

1
Q

How many nephrons per kidney?

A

Approximately 1 million

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2
Q

What is the nephron responsible for?

A

Urine formation

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3
Q

What are the two types of nephrons?

A

Cortical and juxtamedullary

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4
Q

What portion of nephrons are cortical?

A

85%

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5
Q

Where are cortical nephrons found?

A

Lie mainly in the cortex

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6
Q

Where are juxtamedullary nephrons found?

A

Extend deep into the medulla

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7
Q

What are juxtamedullary nephrons important for?

A

The formation of concentrated urine

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8
Q

What are the functions of the nephron and its associated structures?

A

Selectively filter blood, return to blood anything to be kept and carry waste away for storage and expulsion

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9
Q

What is each nephron comprised of?

A

A glomerular capsule, renal tubules and a collecting duct

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10
Q

What is each nephron associated with?

A

A glomerulus and peritubular capillaries

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11
Q

What are glomerular capillaries specialised for?

A

Filtration

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12
Q

What is the structure of glomerular capillaries?

A

Thin walled single layer of fenestrated endothelial cells

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13
Q

What are glomerular capillaries fed and drained by?

A

Arterioles

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14
Q

What is tightly regulated at the glomerular capillaries?

A

Blood pressure

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15
Q

What are peritubular capillaries specialised for?

A

Absoprtion

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16
Q

Where are peritubular capillaries found?

A

Wrapped around the renal tubules (proximal and distal)

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17
Q

What do the peritubular capillaries receive?

A

Filtered blood from the glomerulus via efferent arterioles

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18
Q

What can pass from the peritubular capillaries into the nephron?

A

Some non-filtered solutes that need to be excreted

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19
Q

What are vasa recta?

A

Extensions that follow the nephron loop deep into the medulla

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20
Q

Where are vasa recta found?

A

Only with juxtamedullary nephrons

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21
Q

What is the renal corpuscle?

A

The glomerulus enclosed by the glomerular capsule

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22
Q

What meets at the renal corpuscle?

A

The capillary and nephron

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23
Q

What is the renal corpuscle the site of?

A

The filtration barrier

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24
Q

What is the first part of the nephron?

A

The glomerular capsule

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25
Q

How many layers of the glomerular capsule?

A

Two

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26
Q

What is the layers of the glomerular capsule?

A

Outer parietal layer of simple squamous cells and inner visceral layer of podocytes

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27
Q

What is between the layers of the glomerular capsule?

A

The capsular space which receives the filtrate (primary urine)

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28
Q

Where are podocytes found?

A

Surrounding the glomerular capillaries

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29
Q

What is the structure of podocytes?

A

very branched, very specialised epithelium

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30
Q

What do the branches of podocytes form?

A

Intertwining foot processes called pedicels

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31
Q

What forms between pedicels?

A

Filtration slits

32
Q

What goes through the filtration slits into the capsular space?

A

Filtered blood (filtrate)

33
Q

Where is the filtration barrier found?

A

Between the blood and capsular space

34
Q

What does the filtration barrier allow?

A

Passage of water and small molecules

35
Q

What does the filtration barrier restrict?

A

Passage of most proteins

36
Q

What isn’t filtered into the nephron?

A

RBC’s

37
Q

How many layers are there to the filtration barrier?

A

Three

38
Q

What are the layers of the filtration barrier?

A

fenestrated endothelium of glomerular capillaries, fused basement membrane and filtration slits between the pedicels of the podocytes

39
Q

What is urine?

A

Waste fluid and solutes filtered from the blood

40
Q

What happens to what is filtered?

A

Not everything that is filtered is excreted, some filtrate is reabsorbed and some of what wasn’t filtered is secreted into the nephron

41
Q

What does urine =?

A

Filtered-reabsorbed+secreted

42
Q

What occurs at the PCT?

A

Bulk reabsorption

43
Q

What is the PCT surrounded by?

A

Peritubular capillaries

44
Q

What is the cells of the PCT?

A

Simple cuboidal epithelial

45
Q

What is on the luminal membrane of the PCT cells?

A

Dense microvilli which forms a brush border to increase the surface area for reabsorption

46
Q

How is the basolateral membrane of the PCT cells?

A

Highly folded

47
Q

What does the PCT have lots of?

A

Mitochondria for active transport

48
Q

How is the epithelium of the PCT?

A

Leaky (tight junctions aren’t very tight)

49
Q

Where does the nephron loop go?

A

Down into the medulla

50
Q

Why is the length of the nephron loop important?

A

For production of dilute/concentrated urine

51
Q

What is the nephron loop surrounded by?

A

Vasa recta in juxtamedullary nephrons

52
Q

What are the components fo the nephron loop?

A

Thick descending limb, thin descending limb, thin ascending limb, thick ascending limb

53
Q

What is the structure of the thick descending limb?

A

Similar to the PCT

54
Q

What is the structure of the thin descending limb?

A

Simple squamous epithelium

55
Q

What is the structure of the thin ascending limb?

A

Simple squamous epithelium

56
Q

What is the structure of the thick ascending limb?

A

Similar to the DCT

57
Q

What does the nephron loop have different permeabilities to?

A

Water and sodium

58
Q

What happens at the DCT?

A

Fine tuning (regulated reabsorption)

59
Q

What is the epithelium of the DCT?

A

Cuboidal but thinner than the PCT

60
Q

What is in the structure of the DCT?

A

Few microvilli - no brush border, fewer mitochondria

61
Q

What is reabsorption at the DCT influenced mainly by?

A

Aldosterone

62
Q

What happens at the collecting duct?

A

Fine tuning - regulated reabsorption

63
Q

What drains into a collecting duct?

A

Filtrate from several DCT’s

64
Q

Where does the collecting duct empty into?

A

The papilla

65
Q

What is the structure of the collecting duct?

A

Wall of simple cuboidal epithelium, principal cells and intercalated cells

66
Q

What is the role of principal cells?

A

Reabsorption

67
Q

What is the role of intercalated cells?

A

Acid/base balance

68
Q

What is reabsorption at the collecting duct influenced by?

A

ADH and aldosterone

69
Q

What is the juxtaglomerular apparatus (JGA)?

A

A specialised zone in every nephron

70
Q

Where is the JGA?

A

Where the DCT lies against the afferent arteriole

71
Q

What are the specialised cells of the DCT at the JGA

A

Macula densa cells

72
Q

What are macula densa cells?

A

Chemoreceptors which detect sodium levels in the filtrate in the DCT

73
Q

What are the specialised cells of the afferent arteriole of the JGA?

A

Juxtaglomerular cells

74
Q

What are juxtaglomerular cells?

A

Mechanoreceptors which detect blood pressure

75
Q

What does the JGA control?

A

Glomerular filtration rate, ensuring the system is working at full capacity

76
Q

What does the JGA stabilise?

A

Blood pressure

HUBS192 2024 (38 decks)

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