Vegetative innervation of the human reproductive system in embryogenesis

Relevance. Morphological analysis of the nervous regulation of the functioning of internal organs forms the basis of Russian neurohistology. In addition to the study of the structural and functional organization of the autonomic nervous system (ANS) in adulthood, special attention is paid to the study of ganglion apparatus and the formation of innervation relationships in embryological development, since it is during this period that the foundations of both the normal functioning of all organs and the possible appearance of pathologies in adulthood are formed [1]. To date, extensive material has been accumulated on various aspects of the structural and functional organization of most departments of the internal medicine at different stages of ontogenesis. Of particular interest in recent years is the relationship between the nervous and endocrine systems, as the main regulatory systems of the body, functioning in constant mutual regulation, starting from the moment of their embryonic development. Most of the information about the innervation of the reproductive system in humans has been obtained by methods of classical neurohistology, the development of this department of the ANS during the prenatal period remains less studied. There are only few ultrastructural and histochemical data on the embryonic development of gonad innervation in human embryos, mainly in the second half of the prenatal period. The nervous control of the activity of the gonads determines the endocrine status of the body and has a significant effect on the development of germ cells. Endocrine influences are important factors determining the structural and mediator phenotype of developing neural derivatives of the neural crest. A comparative analysis of the formation of the innervation apparatus of the female and male genital glands in embryogenesis is of considerable interest, since this allows us to clarify the relationship between the influence of different hormones on the development of the nervous apparatus of these organs.

Purpose. The aim of the work was to analyze the development of the nervous system of the female and male human reproductive system during embryonic development. To achieve this goal, the following tasks were set: to study electron microscopically the development of the ganglion apparatus of the genital organs in female and male fetuses in embryogenesis; histochemically and electron microscopically investigate the innervation of the ovaries and testes in the prenatal period of ontogenesis; to conduct a comparative analysis of the development of the ganglion conduction parts of the nervous apparatus of the ovaries and in human embryos. During the research, the following data were obtained: the dynamics of embryonic differentiation of neurons and glial cells, as well as intermalignant relationships in the genitals, were found; the presence of a transitional «adrenergic» phase in the development of neuronal precursors of neurons in the genital ganglion apparatus has been established; small granular cells were not found in the nerve ganglia of the genital organs of human fetuses; electron microscopically showed the presence of nerve fibers in the ovaries and testes in 7-week-old embryos histochemically adrenergic nerve terminals were detected at the 12th week of prenatal development; connections of nerve endings with developing ovarian follicles and forming spiral testes have been investigated; in human spermatozoa, starting from the age of 7 weeks, the presence of a large number of large intermediate Leydig cells with a well-developed smooth endoplasmic reticulum was detected.

Materials and methods. The study was conducted on the material presented by human embryos of both sexes, whose age ranged from 6 to 22 weeks. The embryos were obtained from the gynecological department of the 4th City Clinical Hospital in Saransk. The age of the samples was determined based on obstetric data, weight, body length from crown to coccyx and length from crown to heel. The objects of the study were the organs of the reproductive apparatus: uterus, fallopian tubes, ovaries, seminal tubules, as well as the nerve plexuses surrounding them. The process of fixing the samples began no later than 30 minutes after the surgical intervention performed to terminate the pregnancy. The main research methods used in the article are the standard research method, the methods of classical neurohistology, the electron-histochemical method, the methods of J.P. Transer and G. Richards, the method of V.N. Shvalev.

Results and conclusions. When analyzing the data obtained based on the results of the study, it was revealed that the neural derivatives of the neural crest are determined in the pelvis in the early stages of embryonic development.

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