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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
What is the falciform ligament?
Ventral mesentery between the liver to the anterior wall
26
How does the gall bladder form?
As ventral endodermal thickening/outpouching from bile duct (debate surrounding this)
27
As the liver grows caudally, what happens to the cranial aspect of liver?
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
28
What does most of the mesoderm surrounding the liver go on to form?
Peritoneal (visceral) covering of the liver (except on cranial surface)
29
Around the margins of the bare area, what does the peritoneum reflect off the liver to form?
The coronary ligaments (anterior and posterior)
30
Where the anterior and posterior coronary ligaments meet?
Triangular ligaments at lateral ligaments
31
What are ligaments of the liver formed from?
Mesoderm
32
What is the falciform ligament a remnant of?
Ventral mesentery
33
Why is a liver 10% of total body weight in foetus (5% in adults)?
Importance in haematopoiesis
34
When does the gallbladder start to form?
End of week 3
35
When does the liver start to produce bile?
In week 12 - this is released into the GI tract
36
What is the result of the first bowl movement (meconium) of a newborn?
Dark green in colour (good indicator gall bladder is working)
37
Prior to birth, how is bilirubin removed?
Bilirubin crosses the placenta and is removed by the mother's circulation
38
After birth, how is bilirubin removed?
Liver conjugates bilirubin which is then excreted through the biliary system
39
Why is neonatal jaundice common?
In 60% full term infants the immature liver does not have sufficient glucuronosyltransferase to conjugate bilirubin – hyperbilirubinaemia (jaundice)
40
What is Kernicterus?
A complication of untreated neonatal jaundice Kernicterus is a rare kind of preventable brain damage
41
How does Kernicterus occur?
Excess unconjugated bilirubin (from untreated jaundice) crosses the blood brain barrier and causes brain damage
42
How can newborn jaundice be treated?
Phototherapy
43
What is phototherapy?
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
What do the hepatic and bile duct epithelium undergo?
Rapid proliferation and recanalisation
45
How can biliary atresia occur?
Failure of either duct to recanalise
46
What are the symptoms of biliary atresia?
Causes symptoms that are initially indistinguishable from neonatal jaundice but do not respond to phototherapy
47
Why can biliary atresia present similar to jaunduce?
Build up of bilirubin in biliary system due to atresia
48
What is duplication of the gallbladder caused by?
Caused by an extra endodermal outpocketing during weeks 5 and 6
49
How does the pancreas initially develop?
2 endodermal buds (dorsal and ventral) that fuse together
50
When does the dorsal pancreatic bud appear?
Week 3
51
How does the dorsal pancreatic bud appear?
As an outpocketing of the duodenum that extends into the dorsal mesentery
52
Which pancreatic bud appears first?
Dorsal bud
53
How does the ventral pancreatic bud appear?
As a smaller diverticulum caudal to the developing gallbladder
54
How do the 2 pancreatic buds fuse?
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
When do the 2 pancreatic buds fuse?
Week 6
56
What does the dorsal bud give?
Dorsal bud gives head, body and tail of pancreas
57
What does the ventral bud give?
Ventral bud forms uncinate process
58
How are connective tissue and blood vessels surrounding pancreas formed?
From surrounding mesoderm
59
What is the main pancreatic duct system formed from?
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
How is the minor/accessory pancreatic duct formed?
Accessory pancreatic duct formed from proximal portion of dorsal pancreatic duct
61
What does the minor/accessory pancreatic duct drain?
The main drainage duct of the dorsal pancreatic bud in the embryo
62
Where does the minor/accessory pancreatic duct enter the duodenum?
Minor duodenal papilla
63
What must be noted about the minor/accessory pancreatic duct?
Sometimes obliterated during development
64
Where does the major pancreatic duct enter the duodenum?
Major duodenal papilla (Ampulla of Vater)
65
The ventral pancreatic bud can be bilobed. How does this occur?
Extra endodermal thickening
66
What can a bilobed ventral pancreatic duct cause?
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
How can ectopic pancreatic tissue occur?
Inappropriate differentiation of endodermal cells into pancreatic tissue Can be found in areas ranging from distal oesophagus to tip of primary intestinal loop
68
Where is ectopic pancreatic tissue most common?
Duodenum or stomach mucosa
69
What are dangers of ectopic pancreatic tissue?
Usually asymptomatic Large lesions may cause obstruction, ulceration or haemorrhage (when tissue starts to secrete enzymes)
70
How is the spleen different to most of the abdominal organs?
Not derived from endoderm --> derived instead from mesoderm (as doesn't come from gut tube)
71
When does the spleen appear?
Week 5
72
How does the spleen appear?
A mesenchymal condensation in the dorsal mesentery
73
What does stomach rotation do to the spleen?
Brings the spleen over to the left
74
What does the development of the spleen in the dorsal mesentery cause?
- Gastrosplenic ligament | - Lienorenal (splenorenal) ligament
75
What is the gastrosplenic ligament?
Dorsal mesentery between the stomach and spleen
76
What is the lienorenal ligament?
Dorsal mesentery between the spleen and kidney
77
What is an accessory spleen?
Additional mesenchymal condensations may occur in the dorsal mesentery and form accessory spleens – 10% population
78
Where does an accessory spleen usually form?
Near hilum of primary spleen
79
What are problems of accessory spleen?
Usually asymptomatic but can affect interpretation of medical images and are an important variant for surgeons to be aware of
80
How is the gallbladder formed?
Gallbladder formed from cystic diverticulum from the bile duct

Yr 2 - GI & Metabolism (51 decks)

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