The lymphatic system - a new look at old problems

The lack of adequate methods for the simultaneous detection of lymphatic and blood microvessels in hollow organs does not make it possible to determine the morphological basis of lymph formation and lymph dynamics. In the relevant scientific literature, information about of the structural organization of the lymphatic system, obtained using transmission and scanning electron microscopy, does not provide exhaustive answers to the currently controversial and unresolved issues of the structural organization of the lymphatic microcirculatory bed. The purpose of the study is to presenting data on the organization of the initial lymphatic channel, obtained on the basis of the use of original impregnation methods. Studies were conducted on cats (n=17) and dogs (n=11). The microvascular bed of the intestine and epicardium was identified along with the surrounding tissues by impregnation. On histological preparations, endothelial trabeculae were identified in the lumen of non-muscular lymphatic microvessels of different diameters in the muscular layer and in the submucosa of the intestine. In the muscular layer of the intestinal wall, numerous interstitial channels were found that communicated with open lymphatic capillaries. In the submucosa of the intestinal wall of experimental animals, in addition to the classic capillaries that begin closedly, previously unknown structures were identified - open perivasal lymphatic microvessels and open lymphatic capillaries flowing into them. In the lumen of the perivasal lymphatics are arterioles or arteries. Lymphatic capillaries were in various functional states, which indicates their active peristalsis and suction capacity, which characterize them as utilizers of «biological debris». As a result of the conducted studies, new objective data on the structural organization of the initial lymphatic bed in hollow organs were obtained. The authors showed that the vasomotor activity of the initial lymphatics can serve as a morphological basis for the hypothesis of the initial lymphatic cycle, which consists of a resorption phase and an expulsion phase. The hydrostatic pressure drops in the lumen arising from such a two-phase vasomotor activity of the lymphatics indicate their important role in the process of lymph formation and lymph circulation.