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GI Lectures > Development of the foregut > Flashcards

Development of the foregut Flashcards

1
Q

Where does the foregut start and end?

A

Distal oesophagus and ends halfway along the duodenum (1st and 2nd parts of the duodenum are foregut)

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2
Q

What is the arterial supply to the foregut?

A

Coeliac trunk

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3
Q

What is the innervation from the ANS to the foregut?

A

Sympathetic: Greater splanchnic (T5-T9)
Parasympathetic: Vagus

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4
Q

Where is visceral pain felt from the foregut?

A

Epigastric region

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5
Q

What does the bi-laminar disc form from?

A

Inner cell mass - becomes the human
outer cell mass - becomes the placenta

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6
Q

When does gastrulation occur?

A

In the third week

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7
Q

What is gastrulation?

A
  • Primitive streak forms on the epiblast
  • Epiblast cells migrate to the primitive streak and invaginate through it
  • Some cells displace the hypoblast and form the endoderm
  • Some cells create a new layer between the epiblast (ectoderm) and endoderm = mesoderm
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8
Q

What doe the ectoderm become?

A
  • CNS and PNS
  • Skin, hair and nails
  • Pituitary gland, sweat glands, tooth enamel
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9
Q

What does the mesoderm become?

A
  • Muscle, cartilage and bone
  • Urogenital system, spleen and adrenal cortex
  • Connective tissue of the gut wall, pancreas and liver
  • visceral peritoneum
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10
Q

What does the endoderm become?

A
  • Epithelium of the GI tract, respiratory tract
  • Hepatocytes (cells of liver)
  • Endocrine and exocrine cells of the pancreas
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11
Q

What does lateral folding achieve?

A

Makes us more tubular rather than flat

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12
Q

Where do the lateral folds grow?

A

They grow down and around the yolk sac

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13
Q

What does the paraxial mesoderm layer give rise to?

A

The visceral and parietal layers

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14
Q

What direction does the cephalo-caudal folding occur?

A

Down and in, heading up to leave the yolk sac outside

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15
Q

What is the dorsal mesentery?

A

A fold of peritoneum that attaches to the posterior wall behind the developing gut tube

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16
Q

What determines how the gut tube differentiates?

A
  • It starts to differentiate whilst lateral folding is bringing the ventral body wall together
  • Concentration gradient of retinoic acid starts to specify the different parts
  • lowest levels cranially so near oesophagus and high levels distally
  • Differential expression of transcription factors and genes along the tube specify how regions will develop
17
Q

What are the two mesenteries of the foregut?

A
  • The dorsal mesentery
  • The ventral mesentery
18
Q

Where does the ventral mesentery arise from?

A

It arises from the septum transversum and the liver grows into it and splits it into 2

19
Q

What two spaces does the ventral mesentery become?

A
  • The lesser omentum: connects the liver to the stomach and duodenum
  • The falciform ligament: connects the liver to the anterior abdominal wall
20
Q

Describe the upper 2/3 of the oesophagus

A
  • Striated muscle
  • Innervated by the vagus nerve
21
Q

Describe the lower 1/3 of the oesophagus

A
  • Smooth muscle
  • Innervated by the splanchnic nerves
22
Q

How does the oesophagus come about?

A
  • A respiratory diverticulum is attached to the primitive foregut
  • It grows and pinches so we have 2 separate structures: The trachea and pharynx/oesophagus
  • Then the lung bud appears at the ventral wall of the foregut in the 4th week which become separated from each other
23
Q

What is an abnormal development of the oesophagus?

A
  • Oesophageal atresia (proximal blind-end part of oesophagus, most common and means it doesn’t have full development)
  • Tracheoesophageal fistula (which is an abnormal connection)
24
Q

When does the stomach begin to differentiate?

A

After 4 weeks starts to grow from the primitive gut tube

25
Q

How does the stomach change shape and position?

A
  • Changes shape due to different rates of growth of different parts
  • Changes position - rotates 90 clockwise around its long axis: brings the left side to lie anteriorly and the right side to lie posteriorly
  • Brings duodenum to the right
    (Check Ipad 6th Dec)
26
Q

Where does the liver begin to grow from?

A
  • The liver bud
  • This develops as an outgrowth from the distal foregut
27
Q

When does the liver begin to differentiate?

A
  • Appears in week 3
28
Q

How does the liver begin to develop?

A
  • Cells proliferate: grow into the septum transversum
  • Connection between the liver bud and foregut (duodenum) narrows into bile duct
  • The small stalk-like connection from the liver bud becomes the biliary tree
29
Q

How does the gallbladder form?

A
  • Small outgrowth from the bile duct becomes the gallbladder
30
Q

What happens to the mesoderm when the liver grows?

A
  • As the liver grows, the remaining mesoderm either side becomes membranous > falciform ligament and lesser omentum
31
Q

Where does the pancreas arise from?

A
  • Dorsal and ventral buds arise from the duodenum
  • Dorsal bud develops into the dorsal mesentery
32
Q

How does the pancreas form?

A
  • Rotation of the stomach swings the ventral bud posteriorly
  • Dorsal and ventral pancreatic buds fuse to form the main pancreas
33
Q

What is the final position of the stomach

A

Rotation of the stomach brings its left side to lie anteriorly and swings the duodenum to the right

34
Q

Where is the final position of the dorsal mesentery and what does it become?

A

The dorsal mesentery along the greater curvature bulges down and grows – the greater omentum. This becomes fixed to the mesentery of the transverse colon (and posterior wall).

35
Q

Which organs become retroperitoneal?

A

Some organs are brought into contact with the posterior abdominal wall (e.g., the pancreas and duodenum) and become retroperitoneal

36
Q

How is the lesser sac formed?

A

Organs all start in a position down the midline but due to differential expression and retanoic acid/ other transcription factors the rogans move into final position and the small space behind the stomach becomes the lesser sac

GI Lectures (14 decks)

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