Embryology of the Gastrointestinal Tract

Question 1

What are the three independent parts of the alimentary canal that exist early in embryology?

Answer 1

• foregut
• midgut
• hindgut

Question 2

Describe the foregut.

Answer 2

• forms the distal esophagus, stomach, and part of the duodenum
• ends within the second part of the duodenum, at the entrance of the bile duct

Question 3

Describe the midgut.

Answer 3

• begins at the entrance of the bile duct into the second part of the duodenum and ends with the right 2/3 of the transverse colon
• largest part of the gut

Question 4

Describe the hindgut.

Answer 4

begins with the left 1/3 of the transverse colon, and ends in the upper part of the anal canal

Question 5

Why are the three embryological divisions important?

Answer 5

the adult derivatives of each share a unified blood supply and autonomic nerve supply

Question 6

What is the blood supply to the foregut, midgut, and hindgut?

Answer 6

• foregut: branches of the celiac trunk
• midgut: branches of the superior mesenteric artery
• hindgut: branches of the inferior mesenteric artery

Question 7

What is the sympathetic innervation of the foregut, midgut, and hindgut?

Answer 7

• foregut: greater splanchnic nerves (T5-T9) and lesser splanchnic nerves (T10-T11)
• midgut: greater splanchnic nerves and lesser splanchnic nerves
• hindgut: lumbar splanchnic nerves (L1-L2)

Question 8

What is the parasympathetic innervation of the foregut, midgut, and hindgut?

Answer 8

• foregut: vagus nerve
• midgut: vagus nerve
• hindgut: pelvic splanchnic nerves (S2-S4)

Question 9

What are the autonomic affects on the GI tract?

Answer 9

• Sympathetic activation decreases motility and tone and contracts sphincters.
• Parasympathetic activation increases motility and tone and relaxes sphincters.