Discipline: Veterinary Medicine
The gross and microscopic structures of the trachea were described in 20 Philippine water buffaloes and 15 cattle. Grossly, the similarities between the two species included the relations of the trachea to adjacent structures in the neck and thorax; the number of tracheal cartilages; partial or complete fusion of tracheal cartilage, with the former occurring more frequently and involving two cartilages and the origin of the tracheal bronchus. The differences included a longer trachea with greater diameters and thicker cartilage, and a longer and thicker tracheal carina in Philippine water buffalo. Histologically, both species showed a tracheal wall composed of, from without inward, tunica adventitia, cartilage, tunica submucosa and tunica mucosa. The mucosa was generally smooth and consisted of a pseudostratified columnar ciliated epithelium with many goblet cells particularly in the lateral and ventral walls of the trachea, and a thin highly cellula1·, lymphocyte-infiltrated lamina propria. Other epithelial cells were the basal cells and lymphocytes. The tunica submucosa was dense with many collagen fibers and simple coiled, branched tubuloalveolar predominantly mucous tracheal glands that secreted neutral and sulfated mucins; and a smooth trachealis muscle, which was thicker in Philippine water buffalo. The cartilage layer presented C-shaped hyaline cartilages. The tunica adventitia was loose connective tissue with adipose cells, blood vessels and nerves, and appeared more developed in Philippine water buffalo. The gross and microscopic morphology of the trachea of the Philippine water buffalo and cattle were basically similar and could be used as baseline data in these animals.