This concept covers embryonic folding as the mechanism that converts the flat trilaminar germ disc into a tubular embryo, producing the primitive gut tube (foregut, midgut, hindgut) from the endoderm through cranial-caudal (sagittal-plane) and lateral (transverse-plane) folding. It belongs to human embryology/developmental anatomy, specifically gastrointestinal embryology, and establishes the formal distinction between intraperitoneal organs (suspended by a mesentery, covered by visceral and parietal serosa) and retroperitoneal organs (anchored to the posterior abdominal wall by adventitia, lacking a mesentery), further subdividing the latter into primary and secondary retroperitoneal organs based on whether a mesentery was ever present during development.
This concept covers embryonic folding as the mechanism that converts the flat trilaminar germ disc into a tubular embryo, producing the primitive gut tube (foregut, midgut, hindgut) from the endoderm…