Sublingual and subpharyngeal floor, beak, and palate of the local Egyptian ISA Brown Hen (Gallus gallus Domesticus): gross, morphometric, and scanning electron microscopic features with new insights into their nutritional adaptations.

This study is the first attempt to describe the morphological features of the sublingual and subpharyngeal floor, beak, and palate of the Egyptian ISA Brown Hen using gross and SEM examinations. The rostral part of the lower beak, not occupied by the tongue, was organized into three areas: rostral papillary-teeth-like, non-ridged, and ridged. The sublingual part has a median ridge and two sublingual gland openings; the large round openings are along the ridge, while the small ovoid openings are along each half. The sublaryngeal region contained three sublaryngeal ridges. The oropharyngeal roof papillary system is classified into palatine and pharyngeal (one dorsal transverse row and the two ventral transverse rows) systems. The palatine papillary system has five transverse papillary rows on the choanal field and two longitudinal papillary rows (one on each side of the choanal opening). The choana is divided into a long, narrow rostral part and a wide, short caudal part. The choana is surrounded by an elevated papillary fold of 7-10 small papillae, arranged in a pattern of 2-3 papillae between the transverse ridges. The caudal part is bordered by two longitudinal papillary rows without an elevated border, with 6-8 papillae. A papillary border encircled the choana. There are fifteen ridges on the roof: eight longitudinal and seven transverse ridges. Each lateral longitudinal palatine region carried 6-8 tooth-like rostrally directed projections. Our findings suggested that the oropharyngeal cavity plays a key role in determining how the bird's nutritional mechanism adapts to the Egyptian environment.