Morphological characteristics of the proventriculus of the budgerigar (Melopsittacus undulatus)

The stomach diseases of the parrots, which are one of the most famous companion birds, are frequently encountered, however, information regarding the features of its microscopic structure is insufficient and sometimes contradictory. At the same time, understanding its morpho-functional features is a necessary condition for developing their feeding rations, as well as methods of prevention and treatment of diseases of the digestive system. We determined the peculiarities of the microscopic structure, as well as the age parameters of the morphometric indicators of the proventriculus of budgerigars (Melopsittacus undulatus) of 9 age groups: 1-, 3-, 7-, 14-, 21-days-old, 1-, 2-, and 6 -month-old and 1-year-old. Histological preparations were made from a cross-section of the middle part of the organ, which were stained with hematoxylin and eosin, and according to Mallory as well. The antrum wall of the proventriculus consisted of four membranes: mucous, submucosal, muscular and serous. The superficial glands were found in the composition of the mucous membrane, which were villi-finger-shaped protrusions of the lamina propria, covered with a single-layer prismatic epithelium. Deep glands were located in the submucosal base, which were represented by tightly packed lobes in the shape of a wide cone, consisting of tubular secretory sections that converged radially to the central excretory duct. This opened at the apex of the papillae. We did not establish the muscularis mucosa of the mucous membrane. The muscular sheath consisted of two layers formed by non-striated muscle tissue – an inner wide circular layer and an outer narrow longitudinal layer, between which myenteric nerve nodes were found. Most of the morphometric indicators of the microstructures of the budgerigar's stomach: the thickness of the mucous membrane, the height, and width of the lobules, the width of their tubes, and the height of their epithelium increased from 1-day-old mainly to 1-month-old, and then were smaller. At the same time, the number of lobules of deep glands on stomach cross-sections did not change with age. In contrast, muscle thickness increased from 1-day-old to 1-year-old. An intense increase in the indicators of the superficial and deep glands of the glandular part of the stomach indicates its high functional activity precisely during the active growth and development of budgerigars.