[Staged quality of the transformation of the autonomic nervous system in ontogenesis].

As a result of neurohistochemical and electron microscopic investigations of the autonomic nervous system (ANS) in ontogenesis of the human being and mammalia the premediatory period of its development can be divided into the stage of the nervous crest cells migration into the place of the ganglia anlage and the stage of contact of preganglionic fibers with neural elements. These two stages occur heterochronically. The mediatory period of the ANS development is conditionally divided into five stages. The first is characterized with appearance of mediators in synapses and nervous plexuses in the internal organs. The second--consists in activation of gliocytogenesis and lasts up to 7 months of the human intrauterine life, when the third stage begins--the perinatal maturation of the ANS. In the nervous plexuses myelin fibers appear, perivascular plexuses and structure of the afferent endings become more complex. The fourth stage--completion of the ANS formation--takes place when the child is more than one year of age and it lasts up to sexual maturation. The nervous fibers myelinization is completed, amount of synapses in neurons increases. Then the fifth stage begins--stabilization of the VNS. The postmediatory period takes place not simultaneously in various ganglia of the VNS and has two stages. At first it becomes evident in the sympathetic part of the VNS. Certain morphofunctional manifestations start the stage of the initial exhausion of mediators. In neurons amount of lipofuscin granules grows large, some disturbances in mitochondria and osmiophilic lamellar bodies appear. This stage of the postmediatory period can start early, for example, in the human heart on the fourth decade of life and lasts in the organ up to 60-65 years, when the terminal stage takes place--involutive degeneration of the VNS plexuses.