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

Abstract

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 follicles