The increase and deepening of knowledge about intrauterine development of organs and structures of the male reproductive system becomes an increasingly urgent problem because of the request of clinical medicine. Problems of the histogenesis of the mucous and muscular membrane of the wall of seminal vesicles (SV) in the prenatal period of human ontogenesis have not been given sufficient attention but a number of questions regarding the study of structural reconstruction of the SV wall in the human fetuses of different age groups need further investigation. The purpose of the study is to determine the peculiarities of histogenesis of SV in the prenatal period of human ontogenesis. Materials and methods. The study was performed on 18 serials of consecutive histological slices of human fetuses aged 4-10 months (81.0-375.0 mm in crown-rump length (CRL)). Results and discussion. Peculiarities of structural changes in the layers of the wall of seminal vesicles during the fetal period of human ontogenesis have been studied by means of microscopic method. The epithelium of the mucous membrane of seminal vesicles is represented by cells cylindrical in shape, the height of which is within 10-18 microns in the fetuses aged 4-10 months. Attention is drawn to the fact that at the end of the 4th month of the prenatal period of ontogenesis the mucous membrane of seminal vesicles forms in some places barely noticeable longitudinal folds, followed by a gradual increase in their number and height. The microscopic examination of histological slices of SV in fetuses aged 5 months with CRL 165.0-185.0 mm showed an uneven extension of their cavities. In some areas, the diameter of the last several times exceeds the average size in other regions. Conclusions. At the beginning of the 6th month of intrauterine development (fetuses of 190-205.0 mm in CRL) the microscopic investigation of histological slices of SV revealed some thinning of their wall and a more circular placement of the nuclei of the outer layer of SV wall as compared with the fetuses aged 5 months. At this stage of development folds of the mucous membrane of SV are distinct, unevenly distributed, 20-28 microns in height. Beginning from the 7th month of intrauterine development the folds of the mucous membrane of the seminal vesicles are well-marked and evenly distributed throughout their lumen. The muscular membrane of seminal vesicles consists of the outer longitudinal and inner circular layers. In 4-month-old fetuses the thickness of the outer layer of the muscular membrane is 190-200 microns, and the thickness of its inner layer is 12-15 microns. The subsequent stages of intrauterine development are characterized by a gradual thinning of the muscular membrane and at the end of the fetal period its thickness is only 95-110 microns. In the adventitious membrane of seminal vesicles, which is formed by the fibers of connective tissue, elastic fibers prevail.
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