As evidenced by the publications of recent years, contrary to the existing dogma about the immutability of the state of the enteric nervous system during the postnatal period of ontogenesis, the population of intestinal neurons is a dynamic formation, decreasing with age and changing due to the action of environmental factors. The current article presents the results of study of the microscopic structure of the nerve plexus of the muscular membrane of the enteric nervous system of domestic ducks (Anas platyrhynchos domesticus) of the black white–breasted breed, of nine age groups of 1–365 days of age. The topography, number, area of nerve nodes, as well as the density of neurons in them were determined on transverse sections of the duodenum, jejunum, ileum, caecum and rectum. For the purpose of a generalized assessment of the morphofunctional state of the nerve plexuses, two parameters were determined: the average age indicator of the gut and intestines. The average age indicator of a certain structure of each intestine was determined as the arithmetical average of its nine age indicators. The average age indicator of a certain gut structure was determined as the arithmetic average of the average age indicator of the structure of all five intestines. It has been established that the nerve plexus of the muscular membrane (myenteric, plexus Auerbachi) of the gut of domestic ducks, in contrast to mammals, is not located between the layers of the muscular membrane, but in its outer layer. On a transverse section of the gut wall, the myenteric ganglia and cords that connect have a predominantly elliptical shape. Despite a significant increase with age in the diameter and thickness of the gut wall, the total number of myenteric ganglia changed little, increasing or decreasing with varying degrees of reliability relative to the previous age. In the gut of ducks, during the first year of the postnatal period of ontogenesis, the smallest number of myenteric ganglia was found in the cecum, and the largest – in the ileum. The general pattern of the dynamics of the size of the myenteric ganglia of the gut of ducks was an increase in their area with age. Moreover, this indicator reached the greatest value at different ages of ducks: at 30 days of age in the ileum and cecum, at 180 days of age – in the rectum and at 365 days of age – in the duodenum. The smallest area of the myenteric ganglia was found in the jejunum, and the largest – in the duodenum and ileum. The smallest number of neurons in the ganglion was found in the cecum, and the largest – in the rectum, the lowest density of neurons in the ganglion was found in the cecum, and the largest – in the jejunum. The general quantitative pattern of neurons in the ganglion was the decrease in their density with age. Changes in the morphometric parameters of the ganglia of the nerve plexus of the muscular membrane of the ducks’ gut indicate the plasticity of the enteric nervous system, its ability to dynamically respond to the action of factors of the internal and external environment. It is promising to study the state of the submucous nerve plexus, as well as the cellular composition of the population of neurons of the enteric nervous system of domestic and wild poultry.

There are presented the results of the experimental research of the histological structure of the submucosal nerve plexuses in the intestines of domestic ducks (Anas platyrhynchos domesticus) of 9 age groups from diurnal to 1-year-old of the black White-Breasted breed. The definitions of topography, number, ganglia area, as well as density of neurons in them were determined on cross sections of the duodenum, jejunum, ileum, cecum and rectum. It is defined the nerve nodes and submucosal strands belonging to the enteric nervous system are located between the lamina muscularis mucosae and the inner layer of muscular tunic. In the cross section of the intestinal wall, the submucosal ganglia have the shape of narrow strips. In order to generalize the morphofunctional state of the nerve plexuses, there were determined two parameters: the average age indicator (AAI) of the intestine and intestine. AAI of a certain structure of each intestine was determined as the arithmetic mean of the values of its 9 age indicators. The AAI of a particular intestinal structure was determined as the arithmetic mean of the AAI quantities of the structure of all five intestines. The average number of submucosal ganglia did not increase with the age of the ducks, but changed with varying degrees of reliability in comparison with the previous age. In the intestines of diurnal to 1-day – 1-year-old ducks, the smallest number of submucosal ganglia was found in the cecum, and the largest was found in the rectum. The general pattern of the size dynamics of the submucosal ganglia in the intestines of ducks is an increase with age in their average area. There was found the smallest area of submucosal ganglia in the ileum in the group of ducks of different ages, and the largest was found in the duodenum and cecum. The lowest density of neurons in the submucosal ganglia is found in the cecum, the highest was found in the rectum. Changes in the morphometric parameters of the nerve plexuses ganglia in the intestines of ducks indicate the dynamic nature of changes in the morphofunctional state of the enteric nervous system.