[Embryonic histogenesis of the atrioventricular segment of the heart conduction system of swine (Sus porcus L.)].

Histological, histochemical and neurochemical methods were used in order to study the features of the histogenesis of structures of the atrioventricular area of the conducting system of the heart and the formation of their cholinergic innervation in the postnatal period of the hog. Under study were 175 hearts of embryos of the hog at the age of 3, 4, 5, 6, 8, 10, 12, 14 and 15 weeks and 22 hearts of adult hogs. The formation of different areas of this system was shown to be asynchronous. The atrioventricular fascicle is formed during the 4th week, the atrioventricular node -- during the 6th week and the conducting muscle fibres--during the 8th week of embryogenesis. The fascicle and the node have a complicated structure and different cellular composition. In the process of prenatal ontogenesis the increased amount of glycogen and increased activity of phosphorylase were noted in the cytoplasm of myocytes of the atrioventricular area of the conducting system of the heart. The cholinergic nerve fibres grow up to the structures of the atrioventricular area of the conducting system of the heart during the 6th week of embryogenesis, and by the end of the prenatal development they form a thick network in all its structures.