Micromorphology of Lymph Nodes of Abdominal and Pelvic Organs in Rabbits

The study focuses on a comparative analysis of the micromorphology of lymph nodes in the pelvic and abdominal cavities of clinically healthy California breed rabbits (n = 15). Using histological (hematoxylin-eosin staining), morphometric, and statistical methods, the structural features of the capsule, trabeculae, and hilum of lymph nodes in different locations (jejunal, mesenteric, iliac) were investigated. Histological analysis revealed a distinct layered structure of the capsule, composed of dense collagenous tissue and smooth muscle fibers, providing resistance to deformation. It was established that capsule thickness varies depending on anatomical location: maximum values were found in the mesenteric lymph node (9.78 ± 0.43 μm), while minimum values were observed in the iliac node (5.85 ± 0.59 μm), correlating with the intensity of mechanical stress during peristalsis. At the hilum, the capsule thickens by 24.9-55.4%, attributed not only to the presence of blood vessels, nerves, and the efferent lymphatic vessel but also to increased cellular density (fibroblasts, macrophages). The thickness of the connective tissue trabeculae differed between nodes (20.99 ± 0.77 - 23.18 ± 1.39 μm), reflecting stromal adaptation to dynamic loads and localized immune responses. The results demonstrate a correlation between the structural parameters of lymph nodes and their topography and functional activity, including lymph filtration and lymphoid follicle organization. The obtained data may be useful for developing diagnostic criteria for lymphatic system pathologies (lymphadenitis, neoplasms) in rabbits and for comparative analysis with other livestock species. The study highlights the importance of accounting for anatomical variability when interpreting biopsies in veterinary practice.