Anatomical and topographic patterns of the thymus of black-and-white calves in prenatal ontogenesis

The thymus is the main organ of the immune system, which is responsible for the formation and maintenance of immunogenesis, as well as the proliferation and differentiation of T-lymphocytes. In embryogenesis, the growth and development of the thymus occurs earlier than other peripheral organs of the immune system. Its laying in cattle is carried out in the early period of embryonic development (25-27 days), according to the periodization of life and critical phases of ontogenesis. By the time of birth, the thymus is fully formed and functional. Due to the successful development of immunology, information about the morphofunctional patterns of the organs of the immune system is significantly supplemented. However, despite significant advances in this field of morphology and physiology of immunocompetent organs, many questions, in particular about the structure of the thymus, remain insufficiently studied, especially in productive animals of different species and breeds. The study was conducted at the Department of Animal Anatomy of the St. Petersburg State University of Veterinary Medicine. The material was the corpses of the fruits of black-and-white calves in the amount of seven pieces at the age of 8-9 months of intrauterine development, with an average weight of 20.0 kg. Fine anatomical dissection, morphometry, weighing, and photographing were used as research methods. The aim of the study was to establish anatomical and topographic patterns of the thymus of black– and-white calves in prenatal ontogenesis, as well as to obtain morphometric data. As a result of the study, it was found that the thymus topographically begins from the thirteenth tracheal ring and goes to the third rib and consists of three lobes: cervical, middle, thoracic. The cervical lobe prevails over the middle and thoracic in all linear parameters, except for the width of the thoracic lobe. The intensity of growth of the cervical and thoracic lobes is asynchronous.