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Yr 2 - GI & Metabolism > GI Embryology 3 > Flashcards

GI Embryology 3 Flashcards

1
Q

How do most derivatives of the foregut arise?

A

Outpocketings of the foregut give rise to the organs that assist digestion:

  • Liver
  • Gallbladder
  • Pancreas

These develop from the diverticulum of the cranial half of the duodenum

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2
Q

What is the epithelial lining of the gut tube derived from?

A

Endoderm

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3
Q

What marks the change between embryological forget and midgut?

A

Major duodenal papilla

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4
Q

When does the liver appear?

A

In week 3

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5
Q

How does the liver appear?

A

As an out-pocketing of the future duodenum (why bile duct is connected to gut tube)

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6
Q

What is the name of the liver bud?

A

Hepatic diverticulum (liver bud)

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7
Q

What does the future diaphragm start as?

A

The septum transversum

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8
Q

What does the liver bud contain? What does it penetrate?

A

Contains rapidly proliferating cells that penetrate the septum transversum

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9
Q

Of what origin is the septum transversum?

A

Mesodermal origin

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10
Q

The liver and diaphragm are developing at the same time, what happens?

A

Some mesodermal cells become encompassed in the liver

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11
Q

How does the bile duct form?

A

The connections between the hepatic diverticulum and the duodenum narrows to form the common bile duct

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12
Q

From what germ layer does the liver bud come from?

A

Endodermal thickening

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13
Q

How do hepatocytes (parenchyma) of the liver form?

A

Endodermal cells differentiate into these

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14
Q

Why does the liver also contain some cells derived from the mesoderm?

A

Some mesodermal cells from the developing diaphragm become encompassed in the liver

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15
Q

What mesoderm cells does the liver bud contain?

A

Haematopoietic, Kupffer cells and connective tissue are derived from mesoderm of the septum transversum

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16
Q

What is the function of the liver in the developing embryo?

A

Make blood (haemopoiesis)

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17
Q

What is the first organ to start making blood?

A

The liver

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18
Q

As we develop, what happens to these haemopoietic cells?

A

Move to peripheral organs (liver changes function)

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19
Q

Why is the function of the liver different in embyros?

A

The mother processes nutrients and filtering of blood from digestion and then these nutrients cross placenta

Job of liver is done by mother during pregnancy

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20
Q

The liver continues to rapidly expand. What does this lead to?

A

Midgut has to herniate through into the vitelline duct

Becomes too large to be contained within the septum transversum

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21
Q

When the liver gets too large to be contained within the septum transversum, what does it protrude into?

A

Caudally into ventral mesentery

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22
Q

What does the protrusion of the liver into the ventral mesentery cause?

A

Divides the ventral mesentery into 2 parts:

  • Falciform ligament
  • Lesser omentum
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23
Q

What is the ventral mesentery?

A

How the foregut attaches to the ventral wall

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24
Q

What is the lesser ometum?

A

Ventral mesentery between stomach and liver

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25
Q

What is the falciform ligament?

A

Ventral mesentery between the liver to the anterior wall

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26
Q

How does the gall bladder form?

A

As ventral endodermal thickening/outpouching from bile duct (debate surrounding this)

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27
Q

As the liver grows caudally, what happens to the cranial aspect of liver?

A

The very cranial part of the liver is still in contact with the septum transversum –> close relation to diaphragm

End up with no peritoneal covering –> bare area of liver

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28
Q

What does most of the mesoderm surrounding the liver go on to form?

A

Peritoneal (visceral) covering of the liver (except on cranial surface)

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29
Q

Around the margins of the bare area, what does the peritoneum reflect off the liver to form?

A

The coronary ligaments (anterior and posterior)

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30
Q

Where the anterior and posterior coronary ligaments meet?

A

Triangular ligaments at lateral ligaments

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31
Q

What are ligaments of the liver formed from?

A

Mesoderm

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32
Q

What is the falciform ligament a remnant of?

A

Ventral mesentery

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33
Q

Why is a liver 10% of total body weight in foetus (5% in adults)?

A

Importance in haematopoiesis

34
Q

When does the gallbladder start to form?

A

End of week 3

35
Q

When does the liver start to produce bile?

A

In week 12 - this is released into the GI tract

36
Q

What is the result of the first bowl movement (meconium) of a newborn?

A

Dark green in colour (good indicator gall bladder is working)

37
Q

Prior to birth, how is bilirubin removed?

A

Bilirubin crosses the placenta and is removed by the mother’s circulation

38
Q

After birth, how is bilirubin removed?

A

Liver conjugates bilirubin which is then excreted through the biliary system

39
Q

Why is neonatal jaundice common?

A

In 60% full term infants the immature liver does not have sufficient glucuronosyltransferase to conjugate bilirubin – hyperbilirubinaemia (jaundice)

40
Q

What is Kernicterus?

A

A complication of untreated neonatal jaundice

Kernicterus is a rare kind of preventable brain damage

41
Q

How does Kernicterus occur?

A

Excess unconjugated bilirubin (from untreated jaundice) crosses the blood brain barrier and causes brain damage

42
Q

How can newborn jaundice be treated?

A

Phototherapy

43
Q

What is phototherapy?

A

Phototherapy oxidises bilirubin to a water soluble form that can be easily excreted by the newborn and does not contribute to kernicterus

Blue light is the most effective

44
Q

What do the hepatic and bile duct epithelium undergo?

A

Rapid proliferation and recanalisation

45
Q

How can biliary atresia occur?

A

Failure of either duct to recanalise

46
Q

What are the symptoms of biliary atresia?

A

Causes symptoms that are initially indistinguishable from neonatal jaundice but do not respond to phototherapy

47
Q

Why can biliary atresia present similar to jaunduce?

A

Build up of bilirubin in biliary system due to atresia

48
Q

What is duplication of the gallbladder caused by?

A

Caused by an extra endodermal outpocketing during weeks 5 and 6

49
Q

How does the pancreas initially develop?

A

2 endodermal buds (dorsal and ventral) that fuse together

50
Q

When does the dorsal pancreatic bud appear?

A

Week 3

51
Q

How does the dorsal pancreatic bud appear?

A

As an outpocketing of the duodenum that extends into the dorsal mesentery

52
Q

Which pancreatic bud appears first?

A

Dorsal bud

53
Q

How does the ventral pancreatic bud appear?

A

As a smaller diverticulum caudal to the developing gallbladder

54
Q

How do the 2 pancreatic buds fuse?

A

As duodenum rotates 90° clockwise (as stomach rotates) the ventral bud carried dorsally along with bile duct

I.e. Ventral bud rotates 90° clockwise and fuses with inferior edge of dorsal bud

Their ductal systems become interconnected

55
Q

When do the 2 pancreatic buds fuse?

A

Week 6

56
Q

What does the dorsal bud give?

A

Dorsal bud gives head, body and tail of pancreas

57
Q

What does the ventral bud give?

A

Ventral bud forms uncinate process

58
Q

How are connective tissue and blood vessels surrounding pancreas formed?

A

From surrounding mesoderm

59
Q

What is the main pancreatic duct system formed from?

A

Dorsal duct system fuses with ventral duct system

Main pancreatic duct formed from distal portion of dorsal pancreatic duct and ALL of the ventral pancreatic duct

60
Q

How is the minor/accessory pancreatic duct formed?

A

Accessory pancreatic duct formed from proximal portion of dorsal pancreatic duct

61
Q

What does the minor/accessory pancreatic duct drain?

A

The main drainage duct of the dorsal pancreatic bud in the embryo

62
Q

Where does the minor/accessory pancreatic duct enter the duodenum?

A

Minor duodenal papilla

63
Q

What must be noted about the minor/accessory pancreatic duct?

A

Sometimes obliterated during development

64
Q

Where does the major pancreatic duct enter the duodenum?

A

Major duodenal papilla (Ampulla of Vater)

65
Q

The ventral pancreatic bud can be bilobed. How does this occur?

A

Extra endodermal thickening

66
Q

What can a bilobed ventral pancreatic duct cause?

A

One lobe may migrate ventral to the duodenum and one may migrate dorsally to surround the duodenum – annular pancreas

This can compress the duodenum causing gastrointestinal obstruction

67
Q

How can ectopic pancreatic tissue occur?

A

Inappropriate differentiation of endodermal cells into pancreatic tissue

Can be found in areas ranging from distal oesophagus to tip of primary intestinal loop

68
Q

Where is ectopic pancreatic tissue most common?

A

Duodenum or stomach mucosa

69
Q

What are dangers of ectopic pancreatic tissue?

A

Usually asymptomatic

Large lesions may cause obstruction, ulceration or haemorrhage (when tissue starts to secrete enzymes)

70
Q

How is the spleen different to most of the abdominal organs?

A

Not derived from endoderm –> derived instead from mesoderm (as doesn’t come from gut tube)

71
Q

When does the spleen appear?

A

Week 5

72
Q

How does the spleen appear?

A

A mesenchymal condensation in the dorsal mesentery

73
Q

What does stomach rotation do to the spleen?

A

Brings the spleen over to the left

74
Q

What does the development of the spleen in the dorsal mesentery cause?

A
  • Gastrosplenic ligament

- Lienorenal (splenorenal) ligament

75
Q

What is the gastrosplenic ligament?

A

Dorsal mesentery between the stomach and spleen

76
Q

What is the lienorenal ligament?

A

Dorsal mesentery between the spleen and kidney

77
Q

What is an accessory spleen?

A

Additional mesenchymal condensations may occur in the dorsal mesentery and form accessory spleens – 10% population

78
Q

Where does an accessory spleen usually form?

A

Near hilum of primary spleen

79
Q

What are problems of accessory spleen?

A

Usually asymptomatic but can affect interpretation of medical images and are an important variant for surgeons to be aware of

80
Q

How is the gallbladder formed?

A

Gallbladder formed from cystic diverticulum from the bile duct

Yr 2 - GI & Metabolism (51 decks)

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