3. Embroyolgy - Development Of The Peritoneal Cavity And Forgut Flashcards
What is the primitive gut tube lined with? What is it covered with?
Lined with endoderm.
Covered with splanchnic mesoderm.
What do the foregut, midgut and hindgut begin as before embryonic folding completes?
Foregut and hindgut are blind diverticula.
Midgut is continuous with the yolk sac and so has an opening.
What structures are derived from the foregut?
Oesophagus.
Stomach.
Pancreas, liver, gall bladder.
Duodenum proximal to sphincter of Oddi.
What structures are derived from the midgut?
Duodenum distal to the sphincter of Oddi. Jejunum. Ileum. Caecum. Ascending colon. Proximal 2/3 of transverse colon.
What structures are derived from the hindgut?
Distal 1/3 transverse colon. Descending colon. Sigmoid colon. Rectum. Upper anal canal. Internal lining of bladder and urethra.
What 3 branches of the aorta does GI blood supply come from? What part does each go to, the foregut, midgut, or hindgut?
Celiac trunk - foregut.
Superior mesenteric artery - midgut.
Inferior mesenteric artery - hindgut.
What structure in an exception of the rule in terms of GI blood supply? Why?
Pancreas.
Derived from foregut, but the head is supplied by both the celiac trunk and the superior mesenteric artery.
What is the intraembryonic coelom?
A large cavity formed as the embryo folds.
What is subdivided into the abdominal and thoracic cavities by the further diaphragm?
Intraembryonic coelom.
What does the membrane lining the intraembryonic coelom specialise into as the cavity specialises?
Pericardium, pleural membrane, peritoneum, peritoneal cavity.
What is the mesentry formed from?
A condensation of splanchnic mesoderm.
What mesentery suspends the entire gut tube (foregut, midgut and hindgut) from the dorsal body wall?
Dorsal mesentery.
What mesentery suspends just the foregut from the ventral wall?
Ventral mesentery.
What divides the peritoneal cavity into the left and right sacs?
Dorsal and ventral mesenteries.
What do the left and right sacs become?
Left sac - greater sac.
Right sac - lesser sac.
What is the greater omentum formed from?
Dorsal mesentery.
What is the lesser omentum formed from?
Ventral mesentery.
What does the free edge of the lesser omentum conduct?
Portal triad - herpatic artery, portal vein, common bile duct.
What influences the position of the greater and lesser sacs?
Rotation of the stomach around its long axis during development.
What is a peritoneal reflection?
Any point there is a change in direction of the peritoneum eg from parietal peritoneum to mesentery.
What are retroperitoneal structures?
Structures that are not suspended within the abdominal cavity. Were never in the cavity and never had a mesentery eg kidneys.
What are secondarily retroperitoneal structures?
Structures that began development invested by peritoneum and had a mesentery, but with successive growth and development, the mesentery lost is lost through fusion at the posterior abdominal wall eg pancreas and duodenum.
Where does the foregut extend from in an early embryo during folding?
Lung bud to liver bud.
What forms in the 4th week of development, which leads to the separation of the developing GI and respiratory tracts?
A respiratory diverticulum forms in the ventral wall of the foregut, at the junction with the pharyngeal gut. This forms the respiratory primordium ventrally and the oesophagus forms dorsally, by the formation of the tracheoesophageal septum.
