[Embryonal morphogenesis of the intraorgan circulatory bed, lymphatic outflow pathways and innervation structures]

Development of the circulation bed in human embryogenesis is brought about by a loop-like growth of vessels manifesting in proliferation, integration and morphofunctional transformation of the vascular loops. Proliferation of the loops ensures the blood inflow and reflux at all levels while their integration is followed by formation of hemocirculation system with appearance of the connective and major capillaries which serve the basis for development of true capillaries and capillary network in which precapillary arterioles and postcapillary venules can be distinguished. Hemocirculation system is completed by formation of the arteriolar and venular collaterals and arteriolo-venular anastomoses. Non-participation in the angiogenesis of the autogenic vessel endotheliocytes and their widespread necrosis give grounds to suggest that they are genetically condemned to death. Development of lymph vessels and innervation occurs simultaneously and together with blood vessels by mechanism of their centrifugal growth.