Adrenal Gland of Poultry: Anatomy, Microscopy, Morphometry, and Histochemistry

The adrenal gland plays a crucial role in poultry’s body. Its hormones affect growth, tissue differentiation, and metabolism regulation, as well as the bird body’s resistance to infections, intoxication, stress, and low temperature. For poultry farming, veterinary medicine, and ornithology, it is of scientific interest to study the morphological features of the adrenal gland of birds. This review aimed to assess poultry adrenal anatomy, microscopy, morphometry, and histochemistry by summarizing research data from various published articles. The structure of the adrenal gland has been morphologically investigated in clinically healthy chickens, ducks, geese, and quails. Data from the anatomical level of the adrenal gland have indicated that the shape of this organ in poultry of different species is not the same. In most cases, the shape of the adrenal gland of poultry is close to an oval, triangle, or pyramid. The color of the adrenal gland of poultry varies from gray to brown, which depends on the tissue saturation of this organ with carotenoids. The mass of the adrenal glands of poultry correlates with their age. The left adrenal gland has higher mass, volume, and length indicators than the right gland. The microscopic structure of the adrenal gland corresponds to the general laws of the structure and function of endocrine organs. However, the adrenal glands of poultry are characterized by class features of its histoarchitectonics. The adrenal capsule contains ganglia of the autonomic nervous system, the cell strands of cortical and medullary tissues are intertwined, and the configuration of these cell strands determines the formation of two or three zones of the adrenal gland. Studies of the adrenal glands of poultry at the cellular level have indicated that cortical tissue is represented by acidophilic cells and medullary tissue by basophilic cells. Depending on the shape and electron density of secretory granules, medullary tissue cells are divided into epinephrine and norepinephrine. Data on morphometric parameters (capsule thickness, area of cortical and medullary tissues, cortical-medullary ratio) of the adrenal gland are not the same and depend on the type, age, gender, and sexual activity of poultry. In conclusion, morphologists have paid great attention to studying the features of the anatomy, microscopy, morphometry, and histochemistry of the adrenal gland in clinically healthy poultry. Therefore, the presented data can be used to assess deviations in the morphofunctional state of the adrenal gland in poultry under the influence of various factors and pathology. Keywords: Adrenal gland, Anatomy, Morphological features, Histological and cellular levels, Poultry