Morphological characteristics of the lung in Eurasian teal (Anas crecca): Insights from cross-sectional, casting, histological, and SEM analyses.

This study detailed a comprehensive morphological characterization of the adult Eurasian teal (Anas crecca) lungs through anatomical techniques, including gross anatomy, cross-sectional analysis, corrosion casting, histology, and scanning electron microscopy (SEM). Twenty lungs were examined to identify their topographical position, structural organization, and microarchitecture. Gross anatomical examination showed trapezoidal, non-lobated lungs located craniodorsally within the thoracoabdominal cavity, showing distinct surfaces and borders with seven intercostal tori. Corrosion casting revealed the branching pattern of the bronchial system, highlighting the intrapulmonary primary bronchus (IPPB) and its secondary bronchi, including medioventral (MVSBs) and laterodorsal (LVSBs), interconnected by parabronchi (PB). Seven laterodorsal secondary bronchi (LDSBs) and four lateroventral secondary bronchi (LVSBs) were identified, with posterior secondary bronchi (POSBs) also present along the lateral wall of the IPPB. The POSBs were the shortest, while the medioventral secondary bronchi were the largest. SEM examination showed the spatial arrangement of elongated paleo- and hexagonal neo-parabronchi, characterized by hexagonal architecture and atrial openings leading to air capillaries. Histological examination confirmed the presence of pseudostratified ciliated epithelium in primary and secondary bronchi, smooth muscle layers, and reticular fiber-rich septa separating parabronchi. Two types of hexagonal parabronchi were identified: longitudinally arranged in the paleopulmonic region and circular in the neopulmonic region. The interatrial septa were lined with squamous to cuboidal epithelial cells. These findings enhance understanding of avian respiratory morphology and provide baseline data for comparative anatomical and functional studies in waterfowl species.