Choana Morphogenesis in Developmental Stages of Muscovy Ducks

Abstract

This study was performed by using fourty nine Muscovy ducks to obtained sufficient information about the development of the choanal slit from 1 to 60 days old. The choanal slit formed nearly one third of the total length of the palate in all studied ages; consisted of rostral narrow and caudal wide parts. The ratio of the length of narrow part to the total length of the choanal slit was generally low at the young ducks and increased in the older ones, while that of the wide part reversing the ratio of the narrow part. By SEM, 2 rows of papillae can be identified on the edges of the wide part of the choanal slit in all studied ages. The papillae of those rows were mostly cone-shaped with pointed apices, but some of them are dome-shaped with blunt apices were demonstrated at 60 days old and numerous openings of the intraepithelial glands were scattered within the epithelium of the choanal slit. At the edges of the choanal slit at one day old, the stratified squamous epithelium continues for a short distance before transforming into ciliated respiratory epithelium. This epithelium was interrupted by intraepithelial mucous glands. These glands and their ducts surrounded by multiple lymphatic infiltration and nodules at 15- 60 days old. The lamina propria of the palate at the level of the choanal slit contained palatine salivary glands, these glands in older ages surrounded by numerous lymphatic nodules.