Histological and Histochemical study of Lungs in Domestic Rabbits (Oryctolagus Cuniculus)

Aims: The current study was performed to explore histological features of the lung in the domestic rabbits.Methods: The lung specimens were collected from ten healthy rabbits taken from center at College of Veterinary Medicine / University of Baghdad animal housing. Pulmonary tissue specimens were studied via routine histological techniques.Results: Histological findings revealed division of each bronchus into intra pulmonary bronchi that were frequently divided into primary, secondary and tertiary bronchi. Subsequent subdivision of the last bronchi showed four subdivisions that were primary, secondary, tertiary (terminal) and respiratory bronchioles. The walls of these respiratory passages were showed only mucosa and submucosa tunicae. The epithelial mucosa started from bronchial ciliated pseudostratified columnar epithelium till simple squamous type at alveoli. The tunica submucosa constructed of loose connective tissue in which invested hyaline cartilage segments in the main bronchus then gradually decreased in diameter to smaller and smallest segments. The hyaline cartilage disappeared in all types of bronchioles. The respiratory bronchioles were opened into alveolar ducts which in turn opened into alveolar sacs. Numerous walls’ out-pocketings of simple squamous epithelium lined alveolar duct were observed. Alveolar sac composed of a group of alveoli clusters and the alveolus was just a small space lined by simple squamous epithelium of two types; Type-I pneumocytes (flattened lining cells) and type-II pneumocytes (large lumen-bulged cells with large nuclei).