2 - Embryology of the Foregut Flashcards

1
Q

What is the gut tube?

A

Development in week 3

  • Endoderm internal lining with blind pouch at head and tail
  • Splanchnic mesoderm external lining
  • Opening at umbilicus where yolk sac comes in to form gut tube
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2
Q

What are the parts of each gut and what organs do they go onto form in the body?

A
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3
Q

What is the blood supply to each area of the primitive gut?

A

The structures close to junctions have mixed blood supply

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4
Q

Why do the duodenum and the pancreas have a mixed blood supply?

A
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5
Q

What is the importance of the intraembryonic coelom?

A
  • Space between lateral plate
  • Subdivides into abdominal and thoracic cavities by the diaphragm

- Membrane lining the cavity specialise to become pleura, pericardium and peritoneum

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6
Q

What are the two main mesenteries in the abdominal cavity?

A
  • Dorsal mesentry suspends entire gut tube from dorsal body wall
  • Mesenteries are double layers of peritoneum allowing mobility and a conduit for blood and nerve supply. Formed from splanchnic mesoderm
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7
Q

Where are the greater and lesser sacs and how are they formed?

A
  • Dorsal and ventral mesenteries in foregut divide cavity into left and right

- L: greater sac

R: lesser sac behind stomach

  • Due to rotation of the stomach
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8
Q

What are the omenta?

A
  • Specialised regions of peritoneum
  • Greater: dorsal mesentery
  • Lesser: ventral mesentery (only foregut)
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9
Q

What are the consequences of the rotation of the stomach?

A
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10
Q

What is a peritoneal reflection?

A

Change in direction from parietal peritoneum to mesentry and from visceral to mesentry

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11
Q

What are structures classified as if they are not suspended in the abdominal cavity and therefore have no mesentry?

A

- Retroperitoneal: were never in cavity and never had mesentry

- Secondarily retroperitoneal: begin development in cavity and had a mesentry but with growth the mesentry is lost by fusion to the posterior abdominal wall as organs pushed up against back. Can be mobilised

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12
Q

How does the gut tube split into a GI and a respiratory tract?

A
  • Foregut (lung bud to liver bud)
  • 4th week respiratory diverticulum in ventral wall of foregut at junction with pharnygeal gut
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13
Q

What are some birth defects that can arise from the embryological separation of the oesophagus and the trachea?

A

If the tracheoesophageal septum is in an abnormal position can end up with fistulas and baby is unable to feed and will go blue.

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14
Q

What is the embryological origin of the glands of the foregut?

A

- Liver and Billiary system: ventral mesentry

- Pancreas (Mid and Foregut): uncinate and inferior head from ventral mesentry. The rest from the dorsal mesentry

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15
Q

What relations does the peritoneum have to the liver?

A

- Lesser omentum sits posteriorly attaching lesser curve of stomach to the liver

- Coronary ligament anteriorly between diaphragm and liver

- Falciform ligament separates left and right lobes and at the end the ligamentum teres arises and attaches liver to anterior body wall

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16
Q

Why is the duodenum secondarily retroperitoneal?

A
  • From foregut and midgut
  • Shape determined by rotation of stomach, pushes it to right from anerior, against posterior body wall losing it’s mesentry

- Fusion fascia (double layered peritoneum)

17
Q

What is a summary of the embryology of the foregut tube and the stomach?

A
18
Q

Why is the stomach curved?

A

Dorsal border developed faster forming greater curve

19
Q

Where does the foregut end blindly?

A
  • Oropharyngeal membrane
  • Cloacal membrane
  • Breaks down to form future mouth and anus
20
Q

Is there always a lumen in the digestive tract?

A

No - in 5th/6th week the endoderm (especially in duodenum) proliferates to form solid tube. Recanalised at the end of the embryonic period

21
Q

How does the pancreas develop?

A
  • Dorsal and ventral pancreatic bud
  • Rotation of stomach causes ventral bud to go round the back of the duodenum and join the doral bud.