Initial stages of lymphatic system development in ontogenesis. The investigations history in Russia

Initial stages of development of lymphatic system in ontogenesis were studied in Russia by researchers of Leningrad (St. Petersburg). They consider, that primary lymphatic collectors spring from veins, but lymphatic endothelium has venous nature (one point of view) or mesenchymal nature (another point of view). According first point of view, division of primary veins on secondary veins and primary lymphatic collectors takes place in intimate connection with organogenesis. Under pressure of intensively growing organs arteries with adventitia plunge into lumen extraorganic primary veins together with areas of their endothelial wall. In result of this primary veins are divided on central canal with magistral blood flow and lateral pockets. Lateral pockets of the veins widen with narrowing of their connections with central canal of the veins and come off as lymphatic chinks with endothelial covering. Together with them part of tributaries of primary veins are turned off blood flow. Then lymphatic chinks merge with formation of lymphatic sacs and mesentery lymphatic collectors. Tributaries of lymphatic chinks, and then tributaries of lymphatic sacs become thoracic ducts, lumbar and another lymphatic trunk. Central canal of deformed primary vein acquires adventitia and becomes secondary vein. Later in similar manner blood vessels with more thick walls invaginate into primary lymphatic collectors with thin endothelial walls. In result bud of lymph nodes occurs.