Velopharyngeal closure pattern exerted by contraction of the pharyngeal constrictor muscle in dogs.
OBJECTIVE
This study was performed to investigate aspects of velopharyngeal closure demonstrated by movements of the parapharyngeal wall under various physiological conditions and especially the stimulation of several intrapneumonal receptors.


METHODS
Fifteen mongrel dogs were anesthetized and a nasopharyngeal fiberscope was inserted from the oronasal fistula at the center of the hard palate, with the tip fixed around the choana. Mechanical and chemical stimulation was applied, and ongoing velopharyngeal movements were observed. In each case examined, the muscle nerve located under the bilateral levator veli palatini (LVP) was severed.


RESULTS
Two different closure patterns were recognized between rebreathing and deglutition. Chemical stimulation of the pulmonary irritant receptor and type-J receptor induced a sphincteric tight closure of the velopharynx but only a weak inward movement of the lateral pharyngeal wall at lung inflation.


CONCLUSIONS
The movements of the parapharyngeal wall, mainly represented by the pharyngeal constrictor muscle's contraction, are facilitated as a sphincteric velopharyngeal closure under reflexive movements such as deglutition or gagging.
Tanaka
S
S
First Department of Oral and Maxillofacial Surgery, Osaka University Faculty of Dentistry, Suita City, Japan.
Kogo
M
M
Hamaguchi
M
M
Matsuya
T
T
D000818:Animals; D003679:Deglutition / Q000502:physiology; D004285:Dogs; D004724:Endoscopy; D010160:Palate, Soft / Q000502:physiology*; D010609:Pharyngeal Muscles / Q000502:physiology*; D010614:Pharynx / Q000502:physiology*; D011661:Pulmonary Stretch Receptors / Q000502:physiology; D012123:Pulmonary Ventilation