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BS - Renal System > Embryology of the Kidney > Flashcards

Embryology of the Kidney Flashcards

1
Q

How does the mesoderm become highly organised at day 17?

A

It is split into

  1. paraxial mesoderm (innermost)
  2. intermediate mesoderm
  3. lateral plate mesoderm
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2
Q

What does the paraxial mesoderm go on to form?

A

The majority of the skeleton, skeletal muscles and dermis of the skin

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3
Q

What does the intermediate mesoderm go on to form?

A

The gonads, internal reproductive tracts and the kidneys

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4
Q

What does the lateral plate mesoderm go on to form?

A

The lining of body cavities

This includes the peritoneum of the abdomen

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5
Q

What is the urogenital system?

A

This comprises the urinary system and the reproductive system

They are closely related in development

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6
Q

What are the components of the urinary system?

A
  1. kidneys
  2. ureters
  3. urinary bladder
  4. urethra
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7
Q

What are the components of the reproductive system?

A

Internal and external genitalia

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8
Q

What is the first of three nephric structures that forms?

When does it form?

A

The pronephros

It forms during the 4th week of development

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9
Q

What does the pronephros form from?

A

Intermediate mesoderm in the cervical region condenses and reorganises

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10
Q

What is the role of the pronephros?

A

It develops and regresses without doing anything in humans

Development of the pronephros starts a cascade, leading to development of the 2nd nephric structure

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11
Q

What forms from the pronephros?

When does it disappear?

A

It forms are number of epithelial buds

It disappears around day 25

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12
Q

What forms lateral to the condensements (pronephroi)?

A

The mesonephric duct

At this stage, it is a solid cord of mesoderm and only starts to develop

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13
Q

In which direction does the mesonephric duct develop?

When does it fuse?

A

It forms from intermediate mesoderm in the lower cervical region

It develops caudally

It fuses with the walls of the cloaca on day 26

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14
Q

What is the cloaca?

A

It is a common point at which the GI system and the urinary system are emptied in to

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15
Q

What happens once the mesonephric duct has fused with the cloaca?

A

Canalisation commences from the caudal end

Apoptosis turns the solid cord into a hollow tube

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16
Q

What does canalisation of the mesonephric duct induce?

A

Formation of mesonephric buds from mesenchyme

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17
Q

During which week does the mesonephros form?

A

Week 4

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18
Q

What is the mesonephros derived from?

A

Intermediate mesoderm in the upper thoracic to the upper lumbar regions

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19
Q

How does development of the mesonephric duct affect the formation of the mesonephros?

A

It induces formation of mesonephric buds from the mesenchyme

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20
Q

In what fashion are mesonephric tubules formed?

A

Craniocaudal fashion

As the more caudal tubules differentiate, the cranial tubules regress

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21
Q

What happens to the mesonephric ducts in the thorax and the lumbar region?

A

In the thorax, the buds begin to regress and are broken down

In the lumbar region, the buds develop into mesonephric tubules

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22
Q

What will the mesonephric tubules differentiate into?

A

They differentiate rapidly and lengthen rapidly to form an S-shape and Bowman’s capsule

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23
Q

What forms the glomerulus?

A

The tuft of capillaries that form at the medial end of the tubule

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24
Q

What is the renal corpuscle?

A

It consists of the Bowman’s capsule and the glomerulus

This is the first functional unit in the human urinary system

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25
Q

What happens to the cranial-most mesonephric tubules that fuse with the mesonephric duct?

A

They function between weeks 6-10 to produce a small amount of urine

This is excreted into the amniotic fluid

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26
Q

What happens to the mesonephric ducts after week 10?

A

In the male, they will develop into reproductive structures

In the female, they will regress

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27
Q

What is the function of the mesonephric duct?

A

It acts as a primitive collecting system until is regresses of develops another function

28
Q

How does gonadal development relate to the mesonephric ridge?

A

Gonadal development takes place on the medial aspect of the mesonephric ridge

29
Q

Why is the mesonephric ridge referred to as the urogenital ridge?

A

This includes the mesonephric ridge and the genital ridge

30
Q

What is significant about the metanephros?

A

It will go on to form the definitive adult kidney

It has a dual origin

31
Q

What does the metanephros begin as?

What does it form from?

A

It begins as a specialised bit of mesoderm around the pelvic region

This is the metanephric mesenchyme

it contains undifferentiated cells

32
Q

What does the metanephric mesenchyme fo on to form?

A

EXCRETORY PORTION

  1. Bowman’s capsule
  2. proximal convoluted tubule
  3. loop of henle
  4. distal convoluted tubule
33
Q

What is the role of the mesonephric duct in development of the metanephros?

A

The ureteric bud sprouts from the caudal region of the mesonephric duct

34
Q

What does the ureteric bud go on to form?

A

COLLECTING PORTION

  1. collecting ducts
  2. minor and major calyces
  3. renal pelvis
  4. ureter
35
Q

What happens to the metanephros at day 32 of development?

A

The ureteric buds penetrate the metanephric mesenchyme

36
Q

What happens to the ureteric bud as it penetrates the metanephric mesenchyme?

A

The ureteric bud bifurcates in a specific pattern

This leads to formation of the collecting system

37
Q

What are the stages in bifurcation of the ureteric buds which lead to formation of the collecting ducts?

A
  1. renal ampulla
  2. renal pelvis
  3. major calyces
  4. minor calyces
  5. collecting ducts
38
Q

What is each collecting tubule formed from the metanephric mesenchyme covered with?

A

A metanephric tissue cap

This contains cell clusters

39
Q

What does interaction between the tubule and the metanephric tissue cap cause?

A
  1. specific branching of the tubule

2. differentiation of cells in the metanephric cap to form a renal vesicle

40
Q

What happens to the renal vesicle?

A

It expands to form an S-shaped tubule (nephron) and Bowman’s capsule

41
Q

What happens at the proximal end of the excretory tubule?

A

Capillaries develop in the proximal end of the tubule to form the glomerulus

The proximal end forms the Bowman’s capsule

42
Q

When and why does tissue breakdown occur during development of the metanephros?

A

Tissue breakdown occurs between the 2 embryological origins of the metanephros

This is the excretory and collecting systems

43
Q

What actually forms the definitive nephron?

A

The renal corpuscle, tubule and collecting tubule

44
Q

What causes duplication of the ureter?

A

Premature bifurcation of the ureteric bud

Bifurcation can be partial or complete

45
Q

What is meant by premature bifurcation of the ureteric bud?

A

The ureteric bud pierces the mesenchyme and then it splits

If it splits before it enters the mesenchyme, an extra collecting system may develop

46
Q

What can duplication of the ureter lead to?

A
  1. ectopic ureter (takes a different course and attaches to structures that it shouldn’t)
  2. bifid ureter
47
Q

What causes renal agenesis?

A

Early degeneration of the ureteric bud

OR

failed interaction between the ureteric bud and the metanephric tissue cap

48
Q

What does unilateral agenesis lead to?

A

This is failure of one kidney to form

It is usually asymptomatic

It leads to hypertrophy of the remaining kidney

49
Q

What does bilateral agenesis lead to?

A

It is usually incompatible with life

If not, it leads to Potter sequence

This is a flattened head and failure of limbs to form correctly as they don’t have enough space

50
Q

What is oligohydramnios?

A

Decreased volume of amniotic fluid reduces the space for the developing foetus

This causes the foetus to present with Potter sequence

51
Q

Why does bilateral agenesis lead to a reduced volume of amniotic fluid?

A

Usually the foetus swallows amniotic fluid, and the foetal kidney excretes urine into the amniotic sac

If no urine is secreted, this reduces the volume

52
Q

What are the 2 types of polycystic kidney disease?

A
  1. autosomal dominant

(adult PKD)

  1. autosomal recessive

(congenital PKD)

53
Q

Where do cysts form from in autosomal dominant PKD?

What age group does it affect?

How many births does it affect?

A

Cysts form from all parts of the nephron

Affects 30-50 years of age

Affects 1 in 1000 births

It is not as progressive as recessive PKD

54
Q

Where do cysts form from in autosomal recessive PKD?

What age group does it affect?

How many births does it affect?

A

Cysts form from the collecting ducts

It presents in childhood

It occurs in 1 in 5000 births

55
Q

What happens to the size of the kidneys in polycystic kidney disease?

A

The kidney tries to heal itself and make more structures when the cysts form

This leads to enlargement of the kidneys

56
Q

What mutations are involved in PKD?

A

Mutations in genes of cilia

57
Q

How do the kidneys relocate during development?

A
  1. the metanephric mesenchyme is in the sacral region (pelvis)
  2. growth and elongation of the foetus causes the kidneys to ascend
  3. they reside in a more cranial position in the adult
58
Q

What happens the the blood supply of the kidney as it ascends?

A

As the kidney ascends, it develops a new blood supply more cranially

The original lower vessels degenerate

59
Q

How may someone have more than one renal artery?

A

If the kidney does not lose its blood supply as it ascends

It still develops a new blood supply

60
Q

By which week are the kidneys in their adult position?

A

week 9

61
Q

What causes a horseshoe kidney?

Where does it reside?

A

As the kidneys ascend, the inferior poles fuse together

It resides lower in the lumbar region

62
Q

What are the symptoms of horseshoe kidney?

How many people does it affect?

A

It is usually asymptomatic

It occurs in 1 in 600 people

63
Q

What happens to the cloaca in weeks 4 - 7?

A

The cloaca divides into the:

  1. urogenital sinus (cranial)
  2. anal canal (anorectal region) (caudal)
64
Q

How is the cloaca divided?

A

The urorectal septum grows towards the midline and separates the cloaca

The urorectal septum is a mesoderm derivative

65
Q

What are the 3 distinguishable parts of the urogenital sinus?

A
  1. upper part - presumptive urinary bladder
  2. pelvic part - urethra
  3. phallic part - penile urethra/vestibule
66
Q

What is the bladder initially continuous with?

Why?

A

The allantois

This allows excretions to leave the placenta and enter the mother’s circulation

67
Q

What is formed when the allantois obliterates?

A

The urachus

This connects the apex of the bladder with the umbilicus in the adult

BS - Renal System (8 decks)

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