Gross morphological and histological features of larynx, trachea and syrinx in Japanese quail

This study aimed at observing gross morphological and histological characteristics of the larynx, trachea and syrinx in Coturnix coturnix japonicum (Japanese quail). Sixteen mature quails were divided into two groups. Eight animals were stained with 0.1% methylene blue for 15 min, followed by 50% and 70% ethyl alcohol solution for gross morphological examination. For the observation of histological characteristics the larynx, trachea and syrinx were fixed in 10% formaldehyde and embedded in paraffin. Six-micron sections were stained with haematoxylin and eosin. There were three rows of papillae which were located oral (one row) and aboral (two rows) aspects of the mound. The cricoid cartilage was triangular in shape. Only the inlet of the larynx was covered by the olfactory mucosa whereas the rest was covered by the respiratory mucosa. There were 83-91 tracheal rings which were gradually narrowed from the cranial to the caudal direction. No overlapping occurred between the rings. The last few tracheal rings did not fuse dorsally and formed the tympanium. The pessulus possessed connection with the last tracheal ring and the first bronchial ring. Moreover, it was like a semiprism in shape at the region of bifurcation being vertical in direction. The syrinx was formed by the paired, C-shaped and incomplete bronchial syringeal cartilages. The mucosa of the syrinx was lined with a pseudo-stratified layer of prism-shaped epithelium. There were nine or 14 C-shaped cartilaginous primary bronchi.