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The trachea was made up of 110-116 complete hyaline cartilaginous rings, which extended from cranial larynx to syrinx. The craniocaudal width of the rings progressively increased along the cranial third of the trachea and then decreased caudally. Histologically it was lined by a pseudostratified ciliated columnar epithelium. Lamina propria was made up of loose connective tissue and contained alveolar mucous glands. The submucosa was continuous with the perichondrium of the cartilaginous rings and presented elastic fibres. The overlapping cartilaginous rings were flattened triangular in longitudinal section. Externally, there was a thin tunica adventitia. Trachealis muscle was absent. Sternotrachealis muscle was of striated type.