The macroscopical and microscopical characters of the trachea in different avian species: A comparative study

Abstract

This study aimed to explain and compare the anatomical, histological, histochemical and histomorphometrical analyses of the trachea in different species of birds. This study includes 21 healthy birds from geese (Anser anser domesticus), cattle egrets (Bublucus ibis) and house sparrows (Passer domesticus), 7 seven from each species. Anatomically, the trachea of the goose (the proximal and distal parts) was the longest of all the studied species, yet it had fewer cartilaginous rings than those of the cattle egret. Also, the tracheal length, beside the tracheal muscle in geese plays an important role in the phonation process. Histologically, the trachea is composed of four distinct tunicae: mucosa, propria submucosa, fibrocartilaginous, and adventitia. The epithelium that lined the trachea was ciliated, pseudostratified columnar epithelium (respiratory epithelium) with simple mucous tubuloalveolar glands in either proximal or distal parts depending on the species. The proximal part is made up of overlapped hyaline cartilaginous rings that partially ossified in geese and cattle egrets but did not ossify in sparrows. In the distal part, the overlapping faded in three investigated species.