Table I.
Major embryological events during gut development.
| Embryonic week | Developmental stage |
|---|---|
| Week 3 | - Gastrulation |
| - Primitive gut tube formation | |
| - Elongation and invagination of endoderm anteriorly, caudally, and ventrally | |
| - Development of splanchnic mesenchyme around endoderm | |
| Week 4 | - Discernibility of foregut, midgut and hindgut |
| - Buccopharyngeal membrane resorption | |
| - Invasion of foregut by enteric neural crest cells | |
| Week 6 | - Obliteration of gut lumen |
| - Initiation of midgut herniation through the umbilical ring | |
| Week 7 | - Obliteration of vitelline duct |
| - Completion of enteric neural crest cell migration | |
| Week 8 | - Recanalization of gut tube |
| - Rotation of intraumbilical loop 90° counterclockwise | |
| Week 9 | - Initiation of villus formation |
| Week 10 | - Rotation of midgut 180° clockwise back to the peritoneal cavity |
| Week 11 | - Development of circular and longitudinal smooth muscle layers |
| Week 12 | - Initiation of crypt formation |
| Week 14 | - Formation of mucosal muscle layer |
| Week 24 | - Development of intestinal absorption function |
| Week 32 | - Fetal intestinal absorption equal to adult levels |