10 Embryology Flashcards
Q: During development of an embryo, when does the gut tube start to develop? What is it formed from? (2) How do they grow?
A: from about day 30
The gut tube is formed from two layers of germ line tissue, the endoderm and the mesoderm
The inner layer of the gut is formed from cells in the endoderm
the mesoderm wraps around it to eventually provide structural and functional support
Q: What do cells of the endoderm of the gut tube develop into? (3) mesoderm? (4) What arises separately (2) and from where?
A: mucosal epithelium, mucosal glands and the submucosal glands
lamina propria, gut smooth muscle, blood vessels and the serosa.
The submucosal and myenteric plexus arise separately from the neural crest
Q: What happens a few days after the gut tube starts to develop? Days? What is it possible to do? What starts to develop? how? (3) What continues to grow?
A: some more structures become visible
35-39
It becomes possible to identify which part of the gut tube is where the stomach ends and the duodenum begins
the pancreas starts to develop from two sites. The ventral pancreatic bud sprouts from the liver bud, and the dorsal pancreatic bud sprouts from the duodenum. Even at this early stage it is possible to see that the ventral bud is the smaller of the two.
The liver bud also continues to develop.
Q: As the pancreas continues to develop, what happens? Days?
A: endoderm develops into branched tubules, which later develop into ducts, attached to secretory acini, which is the exocrine portion of the pancreas
40-45
Q: What happens at around 6 weeks? What does this cause? (2) What forms?
A: the gut tube undergoes a primary rotation, which swings the ventral pancreas and the biliary system towards the dorsal pancreas. It also allows the duodenum to form its characteristc C-shape.
Q: What follows the rotation of the gut tube? Describe. Variation in adults?
A: pancreas portions fuse
The ventral pancreas, which is the smaller portion, becomes the uncinate process of the mature pancreas. The ventral pancreatic duct, which is already connected to the biliary tree via the common bile duct.
By this, we mean the gall bladder via the cystic duct and the liver via the hepatic duct, becomes the major pancreatic duct, and the dorsal duct fuses with the common bile duct in most instances.
In some adults it is still connected to the gut as an accessory pancreatic duct.
Q: Where does the endocrine part of the pancreas arise from? what happens to these structures as they grow? (2) amongst?
A: endocrine pancreas (islets of Langerhans) arise from stem cells at the duct branch points
that then disconnect from the ducts to form discrete islands of vascularized endocrine tissue amongst the parenchyma of the exocrine glandular tissue.
