[Anlage of the initial part of the thoracic duct in human embryogenesis].

Canalization of the jugular lymphatic sac is accompanied with disengagement from the blood stream of the thoracic subcardinal and the thoracic parts of the superior mesocardinal veins, forming the paired thoracic anlage of the thoracic duct (ThD). Canalization of the retroperitoneal lymphatic sac (RLS) is combined with differentiation of the antevertebral plexus of the abdominal veins, formation of the ThD cistern. Lateroaortal, retrocaval and retroaortal lumbar trunks (LT) become its roots. Together with RLS and the ThD cistern they form the lymphatic "muff" around the abdominal aorta and inferior vena cava. The degree of its parts separation and its substitution by collaterals of LT and by lymph nodes determines the variants of the definitive organization of the ThD initial part. Already at the stage of anlage the intestinal trunk is not included in the ThD root system, but serves as the RLS anterior tributary, or its lumbar, preaortic tributary.