FEATURES OF THE MICROANATOMY OF THE UMBILICAL VEIN IN THE FETAL AND EARLY NEONATAL PERIODS OF ONTOGENESIS

Studying the microanatomy of the umbilical vein during the fetal period is important because of its critical role in providing the fetus with oxygen and nutrients necessary for normal development. Analysis of the microanatomical features of the umbilical vein allows us to identify the key mechanisms of adaptation of the vascular system to intrauterine conditions, which is important both for fundamental science and clinical practice. Data on age-related changes in the structure of the umbilical vein can help in the diagnosis and prevention of complications associated with placental blood circulation disorders. The purpose of the study is to establish the peculiarities of the microstructure of the umbilical vein during the fetal period. Material and methods. 70 objects of fetuses and 7 newborns were used for the study. To achieve the goal, a complex of morphological research methods was used, which includes macro-microdissection, production of topographic-anatomical sections, radiography, and morphometry. The results. The wall of the umbilical vein in the fetal period has a multi-layered structure, which includes the endothelium (inner shell – intima), subendothelial layer, muscle layer (middle shell – media) and adventitia (outer shell). This structure provides mechanical stability of the vessel and optimal conditions for blood transportation. The endothelial layer of the umbilical vein in fetuses is characterized by a dense arrangement of cells that actively synthesize glycosaminoglycans, which contributes to uniform blood flow and protection of the vessel wall from mechanical damage. The subendothelial layer has a variable thickness, which is associated with adaptive changes to hemodynamic conditions. A large number of fibroblasts and collagen fibers were found in it, which ensure the elasticity and flexibility of the vessel wall. The muscle layer of the umbilical vein is represented by smooth muscle cells that form circularly oriented bundles. This layer plays an important role in maintaining vessel tone and ensuring constant blood flow. The adventitia consists mainly of loose connective tissue that contains blood vessels and nerve fibers that provide metabolic support and innervation of the vein wall. Conclusions. Therefore, in early fetuses, the inner membrane of the wall of the umbilical vein is thin and characterized by a weak development of smooth myocytes, none of the fibers are noted. At the end of the fetal period, all layers of the umbilical vein acquire the greatest development: the outer adventitian layer becomes stronger, the middle layer contains many smooth myocytes, and collagen fibers appear first, and later elastic ones. For the first time, many macrophages, phagocytes, and fibroblasts can be seen in the layers of the umbilical vein wall. In newborns, the number of smooth myocytes and macrophages increases several times, leukocytes and lymphocytes appear.