Abstract: | In 63 series of histological sections of human embryos and prefetuses (4-13 weeks) and in 30 corpses of fetuses and stillborns it has been stated that during the 4th week certain changes occur resulting in formation of the lesser peritoneal sac. It further develops into 3 sections: vestibulum bursae omentalis, bursa omentalis proper and cavity of the omentum majus. Spatial-temporal organization of the lesser peritoneal sac is neither connected with development of separate organs or structures, nor with independent growth, but with the process of development of the whole organocomplex of the upper part of the abdominal cavity, formation of topography and organs' fixation, growth peculiarities of the dorsal mesogastrium. The bursa omentalis proper is forming at the expense of retransformation of the hepatogastric pocket, dependent on growth of the dorsal mesogastrium and on a change in the stomach position. The vestibulum bursae omentalis appears in connection with development and formation of the liver topography, lesser omentum and duodenum. The right pulmoesophagial pocket is interrupted by a developing diaphragm with formation of the superior torsion of the bursa omentalis. Disorders in fixation processes of the organs in the superior part of the abdominal cavity and formation of the bursa omentalis topography can serve as a morphological prerequisite for cysts developing in the retroperitoneal space and hernias of the foramen epiploicum. |