Lecture 8: GI System Embryology

Question 1

What gradient causes transcription factors to be expressed in different regions of gut tube allowing specification?

Answer 1

RA gradient

Question 2

What transcription factor specifies the esophagus?

Answer 2

SOX2

Question 3

What transcription factor specifies the duodenum and pancreas?

Answer 3

PDX1

Question 4

What transcription factor specifies the small intestine?

Answer 4

CDXC

Question 5

What transcription factor specifies the large intestine?

Answer 5

CDXA

Question 6

What initiates the interaction between endoderm and splanchnic mesoderm leading to specification of the gut tube?

Answer 6

Shh

Question 7

What does the right peritoneal diverticulum give rise to?

Answer 7

The lesser sac

Question 8

What does the left peritoneal diverticulum give rise to?

Answer 8

The greater sac

Question 9

Esophageal stenosis, atresia

Answer 9

Narrowed or occluded esophagus due to incomplete recanalization, usually found in lower 1/3

Question 10

Congenital esophageal hernia

Answer 10

Stomach herniating into esophagus

Question 11

Barrett’s esophagus

Answer 11

Acid backing up from stomach changes esophageal lining = pre-cancerous condition

Question 12

Zenker’s diverticulum

Answer 12

Abnormal additional pouch outside of esophagus

Question 13

Hypertrophic pyloric stenosis

Answer 13

Hypertrophic pyloric sphincter causes passageway to be small; takes a couple weeks to present; food never gets into duodenum so no bile in the bolus during projectile vomiting

Question 14

Duodenal atresia

Answer 14

Double bubble sign: air in stomach and duodenum; symptom could be projectile vomiting with bile

Question 15

Duplication cyst

Answer 15

Tubular structure with internal lining of gastrointestinal epithelium, smooth muscle in wall and adherence to alimentary tract

Question 16

Extrahepatic biliary atresia

Answer 16

Incomplete canalization of the bile duct; causes jaundice, dark urine, pale stool; surgical correction or transplant needed

Question 17

What transcription factor induces cells secreting insulin, somatostatin, and pancreatic polypeptide?

Answer 17

PAX4

Question 18

What transcription factor induces cells secreting glucagon?

Answer 18

PAX6

Question 19

Annular pancreas

Answer 19

Ventral and dorsal pancreatic buds form a ring around duodenum which presents as duodenal obstruction

Question 20

Accessory or ectopic pancreatic tissue

Answer 20

Misexpression of PDX1 leads to ectopic expression of pancreas

Question 21

Malrotation of midgut

Answer 21

Abnormally positioned viscera - increased risk of entrapment of portions of intestine; many negative symptoms; most severely septic shock and necrosis of tissue

Question 22

Volvulus

Answer 22

Abnormal twisting of intestine causing obstruction; bloat in dogs

Question 23

Bilious emesis

Answer 23

Green color of bile in emesis; signals obstruction of GI tract below bile duct

Question 24

Situs inversus due to bowel malrotation

Answer 24

Can lead to intestinal ischemia

Question 25

Omphalocele

Answer 25

Herniation of abdominal contents through enlarged umbilical ring; midgut loop fails to return to abdominal cavity - enclosed in pale, shiny membranous sac

Question 26

Gastroschisis

Answer 26

Failure of anterior abdominal wall musculature to close during folding; gut contents NOT surrounded by membrane

Question 27

Ileal/Meckel's diverticulum

Answer 27

Failure of vitelline duct to close; can be symptomatic or asymptomatic; rule of 2's; can cause fistula and fecal discharge through umbilicus

Question 28

Umbilical hernia

Answer 28

Gut pushes skin and fascia out of umbilicus

Question 29

Hirschsprung's disease

Answer 29

Congenital aganglionic megacolon - motor disorder of colon that causes functional intestinal obstruction; failure of migration of neural crest cells that form colonic ganglion cells

Question 30

What are the results of rotation in the gut tube?

Answer 30

1. Changes size of 2 original peritoneal cavities 2. Changes anatomical relationships of organs 3. Causes changes/loss in some of dorsal mesenteries

Question 31

Primarily retroperitoneal organ

Answer 31

Developed outside abdominal cavity which never had a mesentery (such as kidney)

Question 32

Secondarily retroperitoneal organ

Answer 32

Portions of the gut tube whose mesentery fused with lining periotneum

Question 33

Intraperiotneal organ

Answer 33

Organs with a mesentery