title: The Digestive Tract and Derived Primordia Differentiate by Following a Precise Timeline in Human Embryos Between Carnegie Stages 11 and 13.
abstract: The precise mechanisms through which the digestive tract develops during the somite stage remain undefined. In this study, we examined the morphology and precise timeline of differentiation of digestive tract-derived primordia in human somite-stage embryos. We selected 37 human embryos at Carnegie Stage (CS) 11-CS13 (28-33 days after fertilization) and three-dimensionally analyzed the morphology and positioning of the digestive tract and derived primordia in all samples, using images reconstructed from histological serial sections. The digestive tract was initially formed by a narrowing of the yolk sac, and then several derived primordia such as the pharynx, lung, stomach, liver, and dorsal pancreas primordia differentiated during CS12 (21-29 somites) and CS13 (≥ 30 somites). The differentiation of four pairs of pharyngeal pouches was complete in all CS13 embryos. The respiratory primordium was recognized in ≥ 26-somite embryos and it flattened and then branched at CS13. The trachea formed and then elongated in ≥ 35-somite embryos. The stomach adopted a spindle shape in all ≥ 34-somite embryos, and the liver bud was recognized in ≥ 27-somite embryos. The dorsal pancreas appeared as definitive buddings in all but three CS13 embryos, and around these buddings, the small intestine bent in ≥ 33-somite embryos. In ≥ 35-somite embryos, the small intestine rotated around the cranial-caudal axis and had begun to form a primitive intestinal loop, which led to umbilical herniation. These data indicate that the digestive tract and derived primordia differentiate by following a precise timeline and exhibit limited individual variations.
authors.affiliation: Human Health Science, Graduate School of Medicine, Kyoto University, Kyoto.
authors.forename: Saki
authors.initials: S
authors.lastname: Ueno
authors.affiliation: Human Health Science, Graduate School of Medicine, Kyoto University, Kyoto.|Congenital Anomaly Research Center, Graduate School of Medicine, Kyoto University, Kyoto.
authors.forename: Shigehito
authors.initials: S
authors.lastname: Yamada
authors.affiliation: Congenital Anomaly Research Center, Graduate School of Medicine, Kyoto University, Kyoto.
authors.forename: Chigako
authors.initials: C
authors.lastname: Uwabe
authors.affiliation: Deptartment of Anatomy and Embryology, Georg-August-University of Göttingen, Göttingen, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Männer
authors.affiliation: Human Health Science, Graduate School of Medicine, Kyoto University, Kyoto.
authors.forename: Naoto
authors.initials: N
authors.lastname: Shiraki
authors.affiliation: Human Health Science, Graduate School of Medicine, Kyoto University, Kyoto.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Takakuwa
mesh_terms: D002454:Cell Differentiation; D004622:Embryo, Mammalian / Q000166:cytology* / Q000000981:diagnostic imaging; D047108:Embryonic Development; D041981:Gastrointestinal Tract / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000196:embryology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008648:Mesoderm / Q000000981:diagnostic imaging / Q000196:embryology*; D019170:Somites / Q000000981:diagnostic imaging / Q000196:embryology*; D013997:Time Factors
keywords: derived primordial; development; digestive tract; human embryo; timeline