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 threedimensionally 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. Anat Rec,

3D Analysis of Human Embryos and Fetuses Using Digitized Datasets From the Kyoto Collection

“…Such morphometric data are useful for demonstrating the development features at each stage as well as for screening abnormally developed samples. We can select abnormal samples adequately in the liver and digestive tract (Kanahashi et al, ; Ueno et al, ) (Figs. and ; Video 2: https://players.brightcove.net/656326989001/default_default/index.html?videoId=5729925007001; Video 3: https://players.brightcove.net/656326989001/default_default/index.html?videoId=5729925073001).…”

“… 3D reconstructions of the digestive tract and derived primordia in CS13 from ( A ) normal and ( B ) abnormal embryos. We created a precise timeline of events for the development and differentiation of the digestive tract and derived primordia between CS11 and CS13 (Ueno et al, ). (a) Embryo in which the events of differentiation matched the timeline.…”

“…Such morphometric data are useful for demonstrating the development features at each stage as well as for screening abnormally developed samples. We can select abnormal samples adequately in the liver and digestive tract Ueno et al, 2016) Morphometric data, according to human embryonic stages, are also valuable for connecting and comparing sonographic data, which is known as "sonoembryology" (Blaas, 2014). The digital data in our studies could contribute to improvements in prenatal diagnostics by detailing and comparing suitable markers for estimating The liver was not observed; the stomach occupied the majority of the abdominal cavity (arrow).…”

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Blechschmidt Collection: Revisiting specimens from a historical collection of serially sectioned human embryos and fetuses using modern imaging techniques

“…The Blechschmidt Collection has not been subjected to a digitization project thus far. In 2014, some of the present authors from Kyoto University scanned sections in Göttingen and found the specimens to be in suitable condition for research (Ueno et al 2016). On this basis, the decision was made to scan the remaining slides of the Blechschmidt Collection, and the digitization of the collection commenced in 2015.…”