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Abstract

The present study was carried out to investigate the anatomical and histological features of the trachea and lung in an indigenous adult guinea pigs. The current study was conducted on thirty local guinea pigs in both sexes that divided into three equal groups, the first group used for anatomical observations, the second used for cast preparation, while the third one used for histological study. Anatomically the trachea was cartilaginous organ made up of C-shaped cartilaginous rings which attached by an annular ligament. The trachea expands from the second cervical vertebrae level to the 4rth thoracic vertebral level wherever it bifurcates into the right and left principal bronchi. The total number of tracheal rings, total weight and total size of lung, the total length and diameter of the trachea in male were higher than that in female. The resin cast revealed the bronchial tree showed (4) primary bronchi in the right lung and (3) primary bronchi in the left lung. The right lung consists of (4), while the left lung consists of (3) lobes. Histologically the tracheal wall was consisting of four tunicae. The mucosa was lined by pseudostratified ciliated columnar epithelium with goblet cells which positively react with PAS stain. Tunica mucosa was separate from hyaline cartilage by submucosa which contains few tubule acinar mucous glands. The trachealis muscle was attached at the inner side of the rings. The primary bronchi were similar to the trachea but with smaller diameter, and were divided into primary, secondary and tertiary intra- pulmonary bronchi where the cartilaginous rings changes into some plates of hyaline cartilage that disappear in the bronchioles which ends at a terminal bronchioles that directly open in alveolar ductless, alveolar sacs and alveoli while the respiratory bronchioles were absent. The alveoli were open into the alveolar ducts and alveolar sacs. The alveoli lined by type I and II pneumocyte.