3. Development of the GI Part 1 Flashcards
when does the embryo fold
4th week
What is the gut tube?
- Endoderm lined tube
- Runs the length of the body
- Blind pouches at the head and tail ends
- Opening at the umbilicus
- Splanchnic mesoderm covering
Cranio-caudal and lateral folding occur simultaneously. Briefly compare what each of these processes achieve.
Laterally
• Creates ventral body wall
• Primitive gut becomes tubular
Craniocaudally
• Creates cranial & caudal pockets from yolk sac endoderm (beginning primitive gut development)
What germ layer is the gut tube lined with?
Endoderm
compare the foregut, midgut and hindgut at the beginning
- Foregut and hindgut begin as blind diverticula
* Midgut has an opening at first and is continuous with the yolk sac
What germ layers surrounds the gut tube?
Splanchnic mesoderm
What are the 3 divisions of the mesoderm?
1) Intermediate
2) Paraxial
3) Lateral plates - splanchnic + somatic
What is the difference between somatic and splanchnic
mesoderm, in terms of what structures they are associated with?
Somatic - forms dermis + body wall
Splanchnic - forms viscera
What structure is the developing midgut initially connected too?
What structure connects these together?
Yolk sac. VITELLIAN DUCT
What are the derivatives of the foregut?
Oesophagus, stomach, pancreas, liver, gall bladder and duodenum (proximal to entrance of bile duct)
What are the derivatives of the midgut?
Duodenum, jejunum, ileum, caecum, appendix, ascending colon, proximal 2/3 of transverse colon
What are the derivatives of the hindgut?
The distal 1/3 of the transverse colon, descending colon, sigmoid colon, rectum and upper anal canal. And the internal lining of the bladder and urethra
What is the arterial supply to structures of the foregut, midgut and hindgut?
From coeliac trunk, SMA and IMA respectively
What combination of embryonic layers does the Splanchnopleuric mesoderm consist of?
splanchnic mesoderm
visceral peritoneum
gut tube (endoderm)
What combination of embryonic layers does the Somaticpleuric mesoderm consist of?
somatic mesoderm
parietal peritoneum
ectoderm
What term is given to the space that will eventually form the thoracic and abdominal cavity?
Intraembryonic coelom
How is the intraembryonic coelom formed?
Formed as the embryo folds and begins as one large cavity
What divides the intraembryonic caelom?
Divided by the diaphragm into thoracic and abdominal cavities
Rupture Of which membrane creates a mouth opening in the developing embryo? At what point in development does this occur?
Buccophargyneal membrane. 4th week
Rupture Of which membrane creates an anus opening in the developing embryo? At what point in development does this occur?
Cloacal membrane. 7th week
What does the membrane lining the intraembryonic coelom become?
• One membrane lining the whole intraembryonic cavity • Specialises as the cavities specialise o pericardium o pleural membrane o Peritoneum & peritoneal cavity
what is the peritoneal membrane and cavity?
• the peritoneal membrane lines the abdominal cavity a invests the viscera
o during development it grows, changes shape & specialises
o the peritoneal “cavity” is a potential space only
o under normal conditions it should contain nothing
What are mesenteries?
Double layer of peritoneum suspending the gut tube from the abdominal wall
What is the function of mesenteries?
o allow a conduit for blood and nerve supply
o allow mobility where needed