4-6 weeks old embryos´ epithelium proliferates surrounded by thick mesenchyma and fills duodenum (DD) cavity. Epithelial "plugs" are formed under Wirsung´s duct entrances (area of DD lower flexure) and in duodenojejunal flexure. As a result of the turn of pancreas anlages and umbilical intestinal loop, uneven growth of the head of pancreas, these segments of DD are narrowed. Moreover, the mesostenium is rotated, where superior mesenteric artery and vein are. The artery and its branches invaginate into vein cavity, narrow and dismember its peripheral part into lateral recess in 6,5 -8 week old embryos, which troubles blood flow out and causes ischemia of DD paries. Disturbing factors may predicated the excessiveness of DD and vein deformation, ischemia of paries and death of DD epithelium cells, pullulation of connective tissue through its defects into DD cavity, formation of its congenital internal occlusion. As a norm such critical situation in DD development is solve by initiation of lymphatic channel: central channel of superior mesenteric vein gets extima, lateral recess are separateв in the form of lymphatic clefts with endothelial lining. In 8,5-9 week old foetuses they converge into mesenteric lymph tubes, which improve DD paries´ drainage.
The work is presented for an International Scientific Conference "Innovation Medical Technologies", Russia (Moscow), November 17-18, 2009. Received by the editorship on 2.11.2009.