Morphological features of the dorsal and ventral walls of the oropharynx in the common pigeon (Columba livia)

Morphological characteristics of the dorsal and ventral walls of the oropharynx were studied in ten common pigeons. Gross  observation showed that left and right maxillary ramphotheca constituted the lateral boundaries of the dorsal wall of the  oropharynx, while the palate, choana and infundibulum were the prominent structures in this region. The palate, which lacked palatine papillae on its mucosal surface, was characterized by a median palatine ridge and two lateral palatine ridges. The  choanal slit appeared as a roughly triangular opening with a narrow tapered rostral terminus and a broad rounded caudal border. Its cavity was partially demarcated into two compartments by a median ridge. The ventral wall of the oropharynx presented as a concave inter-ramal depression, whose lateral boundaries were formed by left and right mandibular ramphotheca. The caudal surface of the ventral wall of the oropharynx exhibited a mucosal elevation, the laryngeal mound and an oval opening, the  glottis. Histologically, the entire mucosal surface of the oropharyngeal cavity was lined by non-keratinized stratified squamous epithelium. Beneath this epithelium was a dense irregular connective tissue, the lamina propria-submocosa which contained numerous glandular acini, blood vessels, bundles of skeletal muscle fibres, as well as solitary and aggregate lymphoid  follicles. These observations were discussed in relation to the function of the oropharynx in procurement,  maintenance/movement of food in the oral cavity and swallowing of food bolus. It was concluded that the major morphological adaptations of the oropharynx are a reflection of the mode of feeding and nature of diet consumed by the common pigeon.Keywords: Common pigeon, Columba livia, Oropharynx, Palate, Salivary glands, Lymphoid follicle

Histological features of the tongue of the common pigeon (Columba livia)

The study evaluated the histological characteristics of the tongue in ten adult common pigeons, with a view to highlighting the relationship between structure and function of the tongue in the common pigeon. The results showed that the entire dorsal surface of the tongue was covered by a non-keratinized stratified squamous epithelium, while the ventral surface of the tongue exhibited a keratinized stratified squamous epithelium inthe tongue body and apex. In addition, intraepithelial taste buds occurred in the dorsal epithelium of the tongue body and apex. The dense fibrous sub-epithelial connective tissue of the tongue root and body showed presence of mucus-secreting lingual glands and solitary lymphoid nodules. These were absent in the tongue apex. Furthermore, skeletal muscle fibres were abundant in the root and body of the tongue but not in thetongue apex. A paraglossum composed of hyaline cartilage was situated in the core of the tongue, extending from the tongue body to the tongue apex. In longitudinal section, the papillary crest appeared as evaginations of the dorsal lingual epithelium at the boundary between the root and body of the tongue. The evagination, composed entirely of epithelial cells lacked a connective tissue core. It was concluded that these histologicalfeatures are essential adaptations that support the functions of the tongue during food intake, especially in the common pigeon which feeds mainly on grains and seeds.Keywords: Common pigeon, Columba livia, Tongue, Lingual Epithelium, Lingual gland, Intraepithelial taste bu