ACTIVITIES OF SUPERIOR PHARYNGEAL CONSTRICTOR AND LEVATOR VELI PALATINI MUSCLES RELATED TO RESPIRATION IN DOGS

Objective: This study, using mongrel dogs, attempted to delineate the respiratory activity of two closure muscles of the velopharynx, the le vator veli palatini (LVP) and superior pharyngeal constrictor (PC) mus cles. Method: Fifteen mongrel dogs were given tracheotomies, with intr atracheal tubes being connected to their respiratory circuits, Activit ies of the PC and LVP muscles were recorded electromyographically, and the effects of Pao(2) and Paco(2) were analyzed along with the effect s of lung inflation intratracheally with O-2 and N-2. Results: Under h ypoxic conditions, expiratory LVP activity was observed while PC activ ity diminished. The effects of lung inflation on both LVP and PC activ ities were also studied, The activities of both muscles were enhanced by lung inflation,. Conclusion: It was thus suggested that the roles o f both muscles during velopharyngeal closing movements are not the sam e.