Embryology

Question 1

Embryology of the foregut

Answer 1

Around day 30
The gut tube is formed from endoderm and mesoderm
Endoderm - inner layer of gut
Mesoderm - wraps around for structural and functional support
The endoderm includes cells developing into muscosal epithelium, mucosal and submucosal glands
Mesoderm - becomes lamina propria, smooth muscle, vessels and serosa
Submucosal and myenteric plexuses come from neural crest

Question 2

Describe the development of the liver

Answer 2

Day 29-34
The liver develops from the foregut endoderm. Liver bud breaches into the connective tissue mesoderm. The cells start to develop

Question 3

What happens in between days 35-39?

Answer 3

• Can see where stomach ends and duodeunum begins
• Pancreas develops from two sites
• Liver continues to develop

Question 4

Describe the development of the pancreas

Answer 4

• Ventral (smaller) pancreatic bud sprouts from liver bud

- Dorsal pancreatic bud sprouts from the duodenum

Question 5

What happens between days 40-55?

Answer 5

• Pancreas continues to develop
• Liver takes shape
• Gall bladder and biliary ducts are distinguishable
• Endoderm develops into branched tubules which will become ducts
• Islets of Langerhans arise from stem cells at duct branch points that later detach
• Around day 42 the gut tube undergoes a primary rotation
• Ventral pancreas and biliary system are moved towards the dorsal pancreas
• Duodenum forms C shape

Question 6

What happens at around day 56?

Answer 6

• Pancreas portions fuse together
• Ventral pancreas becomes uncinate process
• Ventral pancreatic already connected to biliary tree via common bile duct becomes major pancreatic duct
• Dorsal duct fuses with common bile duct normally (in some doesn’t and remains as an accessory duct)