Embryology of the GI

Question 1

Define gastrulation

Answer 1

A single layered blastula is reorganised into a multi-layered structure known as a gastrula

Question 2

What are the derivatives of the foregut?

Answer 2

• Oesophagus
  
  • Stomach
  • Primary pharynx
  • Lower respiratory tract
  • Pancreas
  • liver and biliary apparatus
  • Duodenum

Question 3

How is the stomach developed?

Answer 3

Stomach rotates 90 degrees and the omental bursa (lesser sac) is formed

Question 4

How is the liver and billary apparatus formed?

Answer 4

Develops from the hepatic diverticulum of the foregut

Question 5

How is the pancreas formed?

Answer 5

• When the stomach rotates 90 degrees the duodenum goes to the right side and the ventricular pancreatic bud goes with it
  
  • The ventral and dorsal bud of the pancreas meet up and the ventral bud becomes the head and the dorsal bud becomes everything else

Question 6

What are the derivatives of the midgut?

Answer 6

• Appendix
  
  • Duodenum (distal)
  • jejunum
  • Caecum
  • Ascending colon
  • 2/3 of the transverse colon

Question 7

How is the midgut developed?

Answer 7

• Herniation: The loops lengthen and infiltrate the umbilical (physiological umbilical herniation)
  
  • Rotation: rotes 90 degrees counter clockwise
  • Retraction: retracts while rotation 180 degrees more counter clockwise

Question 8

What are the derivatives of the hindgut?

Answer 8

• Distal 1/3 of the transverse colon
  
  • Sigmoid colon
  • Descending colon
  • Rectum
  • Upper part of anal canal

Question 9

How can abnormal development of the stomach can result in disease, what causes it and how is it fixed?

Answer 9

• Hypertrophic pyloric stenosis: narrowing of passage between stomach and small intestine
  
  • Could be caused by genetics
    Fixed by surgery

Question 10

What is the abnormal development of the liver and billary apparatus?

Answer 10

Anomalies are rare

Question 11

How can abnormal development of the pancreas result in disease?

Answer 11

• Annular pancreas: the ventricle bud fails to migrate
  
  • This can mean that pancreatic tissue may for elsewhere
  • It can result in duodenal stenosis

Question 12

How can abnormal development of the midgut result in disease?

Answer 12

• Omphalocele: failure of retraction
  
  • Gastroschisis: a muscular defect in the abdomen wall which causes a week area in the umbilicus
  • Abnormal rotation of primary intestinal loops
  • Reversed rotation

Question 13

How can abnormal development of the hindgut result in disease?

Answer 13

• Urorectal fistula
  
  • Rectovaginal fistula
  • Rectoanal atresia
  • Imperforated anus