~ Weeks 4 through 6
Three embryologic divisions of the thoracic and abdominal gastrointestinal tube:
Foregut
Supplied by the celiac artery
Gives rise to the:
Esophagus
Stomach - Liver buds, which ultimately form the liver
Gallbladder
Ventral and dorsal pancreatic buds (aka, diverticula), which will later fuse to form the pancreas
Proximal duodenum
Midgut
Supplied by the superior mesenteric artery
Comprises primary intestinal loop, which connects to the yolk sac via the vitelline duct
Gives rise to the:
Distal duodenum
Jejunum
Ileum
Ascending colon
Proximal 2/3 of the transverse colon
Hindgut
Supplied by the inferior mesenteric artery
Gives rise to the allantois before ending blindly at the cloaca
Gives rise to the:
Distal 1/3 of the transverse colon - Descending and sigmoid colons
The proximal 2/3 of the anorectal canal
INNERVATION
The enteric nervous system, which is derived from neural crest cells, regulates motility to propel the contents of the GI tract.
MESENTERIES
Mesenteries divide the peritoneal cavity and suspend the gastrointestinal tract. Additionally, they provide a protective covering for neurovascular structures.
The ventral mesentery is derived from the septum transversum, and will give rise to ligaments associated with the liver.
The dorsal mesentery secures the gastrointestinal tract to the posterior body wall.
The meso-esophagus attaches the esophagus to the dorsal wall
The mesogastrium anchors the stomach
The mesoduodenum anchors the duodenum
The mesentery proper anchors the primary loop of the midgut
The dorsal mesocolon anchors the hindgut
