Regulation of respiratory airflow during panting and feeding in the dog.

Cineradiographic study of the movement patterns of oropharyngeal and laryngeal structures during breathing and panting in dogs, correlated with recordings of expiratory and inspiratory airflow patterns (via thermocouples) at the nose and mouth show that the soft palate is the principal structural component regulating the path of respiratory in these animals. Cyclical movements of the soft palate during panting are accompanied by complementary movements of the posterior dorsum of the tongue (and epiglottis) to open and to close alternately the oropharynx and nasopharynx. The epiglottis appears to play a passive role during changes in airflow direction; its movements at this time being closely coupled to movements of the posterior tongue and hyoid. The dogs did not breathe during lapping or mastication, indicating the loss of functional separation of respiratory and feeding activities - a role traditionally held for the evolution of a secondary palate in mammals. Food stored in the posterior region of the oral cavity was observed to obstruct airflow via the nasopharynx during food transport and breakdown. Respiration commenced only after the food bolus had been swallowed. We suggest that specializations of the soft palate and epiglottis in dogs for thermal panting appear to restrict the formation of an adequate oropharyngeal seal during feeding.