Начальные этапы развития лимфатической системы человека

Abstract

Abstract Background: the initial stages of the formation of the lymphatic system are not well understood. In the literature, there is still no convincing answer to the main questions – venous or mesenchymal origin, expands its representation centrifugally or centripetally. Material and methods: to obtain information on primary lymphangiogenesis, serial sections of 50 corpses of embryos and fetuses of 5-10 weeks, stained with hematoxylin-eosin, according to Van Gieson and Weigert were studied, supplemented by graphic reconstruction. At the same time, the initial stages of the formation of the lymphatic system were studied in correlation with the remodeling of the embryonic venous beds. Results: it was stated that the formation of the systems of the superior vena cava, inferior vena cava and portal veins is accompanied by partial destruction of the embryonic venous beds. Lymphatic rudiments on the neck, in the thoracic and abdominal cavity, axillary and inguinal-femoral regions are represented by three-dimensional excavations in the connective tissue. They appear in situ on the basis of the collapsing embryonic veins (cavity) and cells of the embryonic connective tissue (primary lining). Accordingly, they have not venous or mesenchymal, but veno-mesenchymal origin. Primary lymphatic structures are formed in situ during the fusion of multiple primordia and differ from them in size and development of the lining of the lymphatic endothelium. These include the jugular, axillary and subtracheal sacs, the right and left prevertebral canals (paired thoracic duct), retroperitoneal and retroaortic sacs of the lumbar region, lateral and subaortic common iliac, external iliac, internal iliac and inguinal sacs, as well as lymphatic canals and sacs basins of branching of the celiac trunk, superior and inferior mesenteric arteries. The primary lymphatic system has a cranio-caudal vector of formation, while the axillary sacs and the prevertebral canals of the chest cavity are connected to the jugular sacs, and the lymphatic structures of the abdominal cavity, in turn, are connected to the latter. The idea of continuous centrifugal proliferation of the jugular and common iliac lymphatic sacs by means of processes has not been confirmed. Not connected to each other and heterochronously forming rudiments and primary lymphatic structures are recorded at 6-9 weeks of gestation. They are fully integrated into a single system in the fetus 10th week. At this time, there are still no intraorgan lymphatic structures and rudiments of lymph nodes. Сonclusions: the lymphatic system has a veno-mesenchymal origin. Lymphatic rudiments, sacs, and canals are heterochronously formed in situ.