Gross morphology and histology of oesophagus in adult emu birds (dromaius novaehollandiae)

Twenty apparently healthy adult emu birds of either sex were utilized for gross and histomorpological observations. The oesophagus was a long, muscular tubular organ with highly distensible tube which is important for easily transport of food from oral cavity to proventriculus. The oesophagus originated from the caudal aspect of the oropharynx and divided into cervical and thoracic parts and no crop was found. The internal surface of the oesophagus was cream colored with number of longitudinal folds. The thickness of the tunica mucosa of cervical and thoracic oesophagus was 50.70 ± 22.62 and 60.70 ± 8.49 µm respectively. The mucous membrane of the oesophagus had irregular folds which was lined by thick non keratinised stratified squamous epithelium with numerous openings of the glands occupied on the sides of the folds. Diffuse and aggregation of lymphocytes also observed in the lamina propria. The oesophageal glands were lined by single layer of columnar cells with small, round basal nuclei, basophilic cytoplasm and clear marked borders. The tunica muscularis was consisted of an thicker inner circular and thinner outer longitudinal layer of smooth muscle. Between these two layer was showed a nerve plexus and associated neurons and blood vessels.