Anatomical and Histological Structure and Morphometric Parameters of the Lungs of the Red Fox (Vulpes vulpes)

The red fox (Vulpes vulpes Linnaeus, 1758) is a widely distributed representative of the family Canidae, characterized by high ecological plasticity and the ability to adapt to diverse natural and anthropogenic environments. Despite its considerable ecological and veterinary importance, the morphofunctional characteristics of its organs remain insufficiently investigated. Particular attention should be paid to the lungs, as they play a pivotal role in gas exchange, maintenance of homeostasis, and adaptation of the organism to environmental conditions. Comprehensive data on the gross and microscopic structure of the lungs are essential for comparative anatomy, veterinary morphology, clinical diagnostics, and experimental research. The aim of this study was to determine the morphofunctional characteristics of the lungs in sexually mature red foxes. Anatomical dissection, gross anatomical examination, histological analysis, morphometry, and statistical data analysis were employed. The lobar organization, topography, shape, linear dimensions, absolute and relative lung weights were assessed. Morphological examination demonstrated that the interlobar fissures were deep and extended to the principal bronchus. All lobes of both lungs were completely separated by fissures and were not connected by pulmonary parenchyma, except for the cranial and middle lobes of the left lung, which were fused dorsally. Organometric analysis revealed that the lungs measured 14.9 ± 0.35 cm in total length, 13.1 ± 0.30 cm in width, and 6.8 ± 0.28 cm in thickness. The lung development index reached 114 ± 0.35%, corresponding to an elongated–expanded morphological type. The bronchial tree originated from the bifurcation of the trachea. Histologically, the bronchial wall consisted of three layers: the mucosa, the fibrous-cartilaginous layer, and the adventitia. Morphometric parameters of the large bronchi were as follows: external diameter, 3478 ± 29 μm; internal diameter, 1750 ± 12 μm; total wall thickness, 864 ± 9 μm, including the mucosa (367.8 ± 7.8 μm), fibrous-cartilaginous layer (404.6 ± 4.8 μm), and adventitia (91.7 ± 1.6 μm). Morphometric analysis also demonstrated statistically significant reductions in all linear parameters of the medium-sized bronchi and terminal bronchioles compared with the large bronchi, reflecting the structural organization of the bronchial tree along successive branching generations. The respiratory portion of the lung parenchyma accounted for 52.74 ± 0.62%, whereas the connective tissue stroma comprised 47.26 ± 0.75%. The mean alveolar volume was 90.4 ± 1.6 × 10³ μm³. The findings of this study expand current knowledge of the gross and microscopic anatomy of the lungs in the red fox and contribute to the comparative anatomy of the respiratory system in carnivorous mammals. These data are of practical value for functional morphology, histology, and veterinary pathology and may be applied in veterinary education, forensic veterinary medicine, and future experimental and clinicopathological investigations. Furthermore, the obtained morphometric data provide a valuable basis for interspecies comparative analyses and for modeling respiratory pathological conditions in veterinary research.