DEVELOPMENT AND FORMATION OF THE TOPOGRAPHY OF THE INFERIOR VENA CAVA AND PULMONARY VEINS DURING THE EIGHTH MONTH OF PRENATAL HUMAN ONTOGENESIS.

Abstract

The aim: To determine the topographic features and morphometric parameters of the pulmonary veins and inferior vena cava in human fetuses during the eighth month of intrauterine development. Materials and methods: A morphometric and histological research of 25 human fetuses in the eighth month of prenatal ontogenesis (271.0 - 310.0 mm parietal-coccygeal length) was conducted. The topographic features of the inferior vena cava and pulmonary veins during the eighth month of intrauterine development were established, and their length and diameter, as well as the change in the angle of their formation, were morphometrically determined. The formation of the topography of these veins is due to the formation of the chest and abdominal organs and continues throughout the entire fetal period of development. Results: The inferior vena cava is formed at the level of the body of the IV lumbar vertebra in the eighth month of the intrauterine period of human development. The initial part of the trunk of the inferior vena cava obliquely "crosses" the common iliac artery from the left to the right. At this level, the vein is located to the right and slightly behind the aorta. In fetuses of the given age group, the right adrenal gland borders the inferior vena cava only at the level of the lower 2/3 of its medial edge. At the level of the subhepatic section of the inferior vena cava, 4-5 pairs of lumbar veins flow into it. In most cases, the ductus venosus flowed into the inferior vena cava independently between the middle and left hepatic veins. Compared to other sections of the inferior vena cava, the lumen of its diaphragmatic section, which passes through the opening in the dorsal part of the tendinous center of the diaphragm on the right, increases. During this period, it was established that the pulmonary veins lie completely in the heart cavity and are surrounded by a serous membrane. In all fetuses, two pulmonary veins flow from each lung into the left atrium. The level of confluence of the venous ducts of the pulmonary veins and their number varies individually. Pulmonary veins and their ducts lie more superficially and do not repeat the passage of the corresponding bronchi and arteries, lying, as a rule, within the limits of interlobular, intersegmental, and intersubsegmental connective tissue membranes. Conclusions: In this age group, changes in venous vessels and complications in the structure of their walls and their ducts continue. The passage and branching of the bronchial tree and arterial branches (starting with the segmental branches) are almost completely identical. A significant increase in the number of small ducts was found in the system of pulmonary veins. There is an increase in the morphometric indicators of the size of the inferior vena cava in comparison with its other parts. In the wall of the pulmonary veins and inferior vena cava, all three tunics are clearly visible, which in structure are close to the definitive one.