Early Gut Tube & Mesenteric Attachments
~ 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
- 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
- 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