3 - Development of the Gut Flashcards
What do I need to know?
- Define fore/mid/hindgut
- Structures that originate from fore/mid/hindgut
- Describe the development of the gut
- Explain the major congenitial anomalities associated with the development of the gut
What is an example of structures that began as intraperitoneal and have become retroperitoneal?
Parts of the small and large intestines
Arterial supply to fore/mid/hindgut?
Foregut = Celiac Artery Midgut = Superior Mesenteric Artery Hindgut = Inferior Mesenteric Artery
A ligament refers to …
2 layers of peritoneum that connect 2 organs or an organ to the body wall
Mesenchyme?
Non-specialised embryonic stem cells
Hypoblast becomes …
Epiblast becomes …
Endoderm
Ectoderm
How does embryo development occur?
Longitudinal and lateral folding
How do the ectoderm and mesoderm fold?
Laterally and ventrally
> They then meet centrally closing off the endoderm to from a separate gut-tube structure
What do each of the layers end up forming?
Endo - epithelial lining of the tube
Meso - supporting structures and smooth muscle/musculature of the gut tube
Ecto - outer tissue layer
Space in between the mesoderm layers - body cavity/greater sac
What causes the folding?
The ectoderm (and mesoderm) cells proliferate much faster outwards than the endoderm so it wraps AROUND and down
What happens to the yolk sac?
The mesoderm pinches in the yolk sac to form a separate gut tube (endoderm > mucus membrane)
Longitudinal Folding?
- draws the opening of the gut tube to the yolk sac closed (like a purse string)
- divides the anterior gut tube and posteiror gut tube (fore and hindgut) while the midgut remains open to the yolk sac
- further longitudinal folding means the communication with the yolk sac gets smaller and the regions become more refined
Membranes at cranial and caudal ends?
Oropharyngeal membrane from the ectoderm of the stomodeum
Anal membrane from the ectoderm of the anal pit
Describe what happens to the lumen of the gut tube during development
Initially patent. As the epithelium proliferates it plugs up the lumen of the gut tube. At week 8 by the end of the embryonic period recanalization occurs, it loses patency and re-opens
Gut supply to foregut?
Celiac Trunk
Gut supply to midgut?
Superior Mesenteric Artery (also continues into the yolk sac)
Gut supply to hindgut?
Inferior Mesenteric artery
How does knowing the arterial supply help with knowing the ANS and lymphatics?
ANS follows the arterial supply and deep lymphatics follow the arteries
Describe the development of the oesophagus
- is immediately caudal to the pharynx
- partitions/divides from the trachea (ventral)/respiratory diverticulum
- initially short but rapidly elongates
- also plugs and recananalizes
What is a diverticulum?
A usually abnormal sac or pouch formed at a weak point in the wall