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GI > GI Embryology > Flashcards

GI Embryology Flashcards

As usual, erring on the side of too much detail... I don't love Kessler's embryo lectures.

1
Q

What structure becomes the umbilicus? What does it do?

A

Vitelline duct - maintains continuity with yolk sac.

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2
Q

What structure seals the future site of the oral cavity?

A

The buccopharyngeal membrane

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3
Q

What invaginates and seals to capure the gut lumen? What does the part that fuses become?

A

Yolk sac roof folds down…. captures lumen of gut tube.

Fuses at the ventral midline.

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4
Q

What structure seals the future site of the rectum?

A

The cloacal membrane

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5
Q

What happens to the gut tube before you get the “definitive hollow gut”? 3 things that can go wrong here?

A 
It starts hollow, is occluded by endodermal proliferation, then recanalized.
3 problems:
Duplication (creating a flap thing).
Stenosis.
Atresia (complete blockage of tube).
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6
Q

What are the major arteries that supply thoracic foregut, abdominal foregut, midgut, and hindgut?

A

Thoracic foregut: aortic arches.
Abdominal foregut: Celiac trunk
Midgut: Superior mesenteric artery
Hindgut: Inferior mesenteric artery

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7
Q

Review: Where does midgut start?

A

Right at the ampulla of Vater.

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8
Q

Review: Where does the hindgut start?

A

The distal 1/3 of the transverse colon.

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9
Q

Where do the lungs come from? (among the things mentioned in this lecture)

A

Thoracic foregut.

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10
Q

What is esophageal atresis and stenosis? What causes it?

A

Blockage or narrowing of esophagus.

Usu. due to failure of recanalization.

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11
Q

What is tracheoesophageal fistula?

A

Caudal displacement of septum between trachea and esophagus. (there’s a better description of this in the esophageal and gastric pathology lecture)

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12
Q

What is congenital hiatal hernia? What causes it?

A

Part of stomach is herniated into thoracic cavity.

Caused here by a failure of the esophagus to elongate.

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13
Q

So the gut has dorsal and ventral mesenteries. Which extends all the way? Which is only part way, and how part does it go?

A

Dorsal mesentery is on whole length of gut.

Ventral mesentery is just on the foregut.

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14
Q

Which side of the stomach becomes the greater curvature? How does this rotate?

A

Dorsal becomes greater curvature (and dorsal mesentery becomes greater omentum).
Rotates 90 degrees such that greater curvature faces left.

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15
Q

What change in the mesentery helps drive stomach rotation?

A

Differential thinning of the dorsal mesentery.

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16
Q

What is duodenal atresia and stenosis?

A

Just like in esophagus, failure of recanalization causes blockage / narrowing.

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17
Q

What does duodenal atresia look like on ultrasound? Why?

A

“Double-bubble” - because stomach and proximal duodenum are dilated with stuff that can’t get through.

18
Q

What spaces does the rotation of the stomach define? What connects these two spaces?

A

This defines the lesser sac dorsal to the stomach (and… the rest of the peritoneum).
They’re connected by the epiploic foramen.

19
Q

What develops on the ventral surface of the proximal duodenum (day 22)?

A

The hepatic plate/diverticulum

20
Q

What connects the liver to the stomach?

A

Lesser omentum (ventral mesentery)

21
Q

What connects the liver to the body wall?

A

The falciform ligament.

22
Q

So the cystic diverticulum…

A

Grows, if not off of, pretty near the hepatic diverticulum… which makes sense.

23
Q

2 anomalies of liver and cystic ducts?

A

Gall bladder duplication - usually asymptomatic.

Extrahepatic biliary atresia - failure to canalize.

24
Q

How does the pancreas form?

A

As two buds, dorsal and ventral, which fuse together.

25
Q

Which duct becomes the main pancreatic connection to the duodenum?

A

The ventral duct.

26
Q

What is annular pancreas? Why is this a problem?

A

Ventral and dorsal buds fuse such that they wrap around the duodenum, blocking it off or causing stenosis.

27
Q

Where does the pancreas end up?

A

Dorsal mesentery gets fixed onto dorsal body wall… most of it becomes “secondarily retroperitoneal.”

28
Q

Which gut structures are secondarily retroperitoneal?

A

Duodenum, pancreas, colon.

29
Q

Which gut structures are intraperitoneal?

A

Stomch, gallbladder, transverse colon.

30
Q

Which gut structures are retroperitoneal?

A

Thoracic esophagus, rectum.

31
Q

Where does the primary intestinal loop (the part that becomes ileum and large bowel) go? How does it rotate?

A

Herniates out into umbilical region and rotates.
Cranial part goes 90 degrees right.
Caudal part goes 90 degrees left.

32
Q

What happens when the primary intestinal loops retracts?

A

It rotates 180 degrees, bringing it to the final, adult position.

33
Q

What’s the difference between a congenital omphocele and an umbilical hernia?

A

In congenital omphocele, the midgut never retracted out of the umbilical cord.
In umbilical hernia, the midgut retracted, but the umbilicus didn’t fully close, and stuff re-herniated.

34
Q

What is gastroschisis?

A

Midgut structures extrude through the ventral body wall. (doesn’t include umbilicus)

35
Q

What is Ileal (Meckel’s) Diverticulum?

A

Remnant of the yolk stalk persists as outpouching. Can contain gastric or pancreatic tissue, causes appendicitis-like symptoms.

36
Q

What can happen if proper rotation doesn’t occur?

A

Things can twist (volvulus) and occlude eachother.

37
Q

What separates the rectum from the urogenital sinus early on?

A

The urorectal septum - forms in the cloaca.

38
Q

What’s the visible junction between the ectoderm and endoderm in the anus?

A

The pectinate line

39
Q

Review: What causes congenital megacolon (Hirschsprung’s Disease)?

A

Dilatation of colon - no peristalsis because there are no ganglia. (Neural crest cells failed to migrate)

40
Q

What’s membranous atresia?

A

Failure of anal perforation… easy to fix with surgery.

41
Q

In aganglionic megacolon, which part is dilated?

A

The part of the colon proximal to the aganglionic area is dilated.

GI (45 decks)

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