Abstract
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.
Highlights
The enteric nervous system is the largest and most complex autonomous part of the peripheral nervous system, which together with the enteroendocrine and immune systems and when exposed to the microbiome under the control of the central nervous system regulates the vital functions of the digestive tract, including digestive, immune, hormonal and metabolic functions (Kulkarni et al, 2018; Pawolski & Schmidt, 2020; Spencer & Hu, 2020)
Auerbachi) appears in the outer – longitudinal layer of the muscular membrane. Such plexuses are represented by clusters of neuronal bodies – nerve nodes and bundles of nerve fibers that connect
In the wall of the glandular part of the stomach of ducks (Anas platyrhynchos) ganglia of the myenteric plexus were found between the layers of the muscular membrane (Mirabella et al, 2003), and in the wall of the muscular part of the stomach of chickens – directly under the serous membrane and in its circular layer (Gabella & Halasy, 1987)
Summary
The enteric nervous system is the largest and most complex autonomous part of the peripheral nervous system, which together with the enteroendocrine and immune systems and when exposed to the microbiome under the control of the central nervous system regulates the vital functions of the digestive tract, including digestive, immune, hormonal and metabolic functions (Kulkarni et al, 2018; Pawolski & Schmidt, 2020; Spencer & Hu, 2020). Innervation allows the organs of the intestinal tract to respond to various stimuli by regulating motility and secretion, as well as influencing the physiology, behaviour, and immunity of the whole organism (Ameku et al, 2020; Logvinova et al, 2020). Neurocytes of the enteric nervous system are located mainly in the form of small clusters – ganglia, which maintain neuronal continuity with each other, forming two separate ganglion plexuses – the submucosa and the muscular membrane (myenteric, plexus Auerbachi). Isolated neurons are widespread in the gut wall (Aisa et al, 1990; Ameku et al, 2020)
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