Soft palate movement during sucking behavior.

To clarify the aspects and role of oropharyngeal closure, soft palate movements during sucking were observed and then assessed by electromyographic and fluoroscopic analyses. Three patterns of sucking movements by the palatoglossus and levator veli palatini muscles were analyzed with electromyographic means in seven healthy adults. Furthermore, a forced sucking maneuver, which required special effort to produce a strong sucking pressure by opening the jaw, was analyzed using lateral fluoroscopy in three of the subjects. During all tested sucking movements, the palatoglossus muscle showed continuous activity. The levator veli palatini muscle did not show remarkable activity during regular air sucking or water sucking when water was held in the oral cavity. However, its participation increased when intraoral sucking pressure was increased by opening the jaw, and lateral fluoroscopic examinations revealed that the soft palate was pulled toward the oral cavity to form a tight contact between the rostral portion of the soft palate and the retrotongue, causing the soft palate to make an "L" shape. The palatoglossus muscle plays a major role in palatal movement during sucking. Furthermore, the levator veli palatini muscle, whose activity was observed only during high-pressure sucking with an open jaw, may act to maintain tension in the soft palate against strong negative pressure in the oral cavity.