MORPHOGENESIS OF DUODENUM IN EARLY PERIOD OF HUMAN ONTOGENESIS

Antonyuk O. P., Vovk Yu. M.

MORPHOLOGY

Scentific article

The embryos of 4.5 mm of parietal-coccygeal length (PCL) throughout the primary intestinal tube and the rudiments of the duodenum, in particular, exhibit a well-defined lumen. During this period of development, there is a lumen in the primary intestine, where as in the embryos 5.5-6.0 mm PCL at the level of the common bile and dorsal pancreatic ducts there is a temporary narrowing of the lumen and separate vacuum-like cavities are formed, and in places of transition of the stomach closure of the opening, the so-called epithelial adhesion of the lumen of the intestine. In the embryos of 5.0 mm PCL in the central part of the duodenum begins determine a single cavity. The epithelial layer lies on the formed basement membrane, which is expressed in the intestine, facing the body cavity. Epithelial cells have a high prismatic shape and in separate sections of the duodenum lie in 3-4 rows. At the beginning of the pre-fetal period (pre-fetal of 14.0-20.0 mm TCD), there is an intensive growth of the upper and mesenteric parts of the duodenum. The intestine rotates dorsolaterally, and at the level of the pancreas is placed dorsomedially and directed downwards. The muscular membrane of the duodenum at this stage of development is represented by a layer of circular-oriented collagen fibers, their apical part. The upper and lower parts of the duodenum have the appearance of an arc, located in the sagittal plane and open in front. The initial section of the duodenum, including its future descending portion, is directed backward, perpendicular to the spinal column, and the lower portion, which passes into the twelve-inch bend and further into the proximal knee of the intestinal loop. At the end of the pre-fetal period, villi are formed in the duodenal wall, which are formed by the reduction of physiological atresia, and the rupture of the epithelial septum leads to the epithelial covering of the villi. In 11.5 weeks of pre-fetal development in the area of the duodenum wall, the height of the epithelium reaches 29.0+0.5 μm, the thickness of the submucosa – 36.0±1.5 μm. Muscle thickness is characterized as the sum of the thickness of the circular and longitudinal layers, with the circular layer reaching 19.0±0.7 μm, the thickness of the longitudinal layer – 21.0±0.5 μm. In the area of the villi, there is also an increase in metric indices of all structures of the intestine except the serous membrane. The height of the epithelium increases and reaches 30.0±0.5 μm. In the period from 11.5th to 12.0th weeks of prenatal development is of interest in terms of assessing the formation of the main structures of the membranes of the duodenum. This period is characterized by some slowing of the processes of neoplasm and differentiation of the villi, which is confirmed first of all by the slowing of the rate of increase of the size of the papillae of the mesenchyme in comparison with the previous stage. By the end of the 12th week of intrauterine development, the formation of layers and membranes of the wall of the duodenum continues. The lumen of the intestine has a stellar shape due to the large number of primary villi. The lining of the lumen is represented mainly by a single-layer high prismatic epithelium. Therefore, the duodenum is formed from different parts of the primary intestine, namely: cranial area – from the terminal segment of the anterior intestine; caudal – from the middle intestine or from the «umbilical loop» from its front knee. The enlage of the duodenum is fixed by a short ventral mesentery, hepatic-duodenal joint with common bile duct and dorsal mesentery and pancreas. The initial stage of physiological atresia of the duodenum is observed in embryos of 5th weeks (5.5-6.0 mm TCD) at the site of transition of the stomach into the marked intestine, and complete physiological atresia is observed in embryos of 6th weeks (11.5-13.5 mm TCD) when the lumen is completely covered by the closure of the distal part of the intestine. The process of recanalization of the lumen of the duodenum – occurs during the 7th week (14.0-20.0 mm TCD) and ends at the end of the 8th week (20.0-25.0 mm TCD) embryogenesis.

embryogenesis, duodenum, human

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«Bulletin of problems biology and medicine» Issue 3 (152), 2019 year, 278-282 pages, index UDK 616.364.007.271

10.29254/2077-4214-2019-3-152-278-282