الفهرس 
Classification and etiology of Velopharyngeal DysfunctionOnly 14 pages are availabe for public view
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Abstract
Normal velopharyngeal closure is accomplished by the coordinated action of the velum (soft palate), the lateral pharyngeal walls, and the posterior pharyngeal wall. These structures function as a valve that serves to close off the nasal cavity from the oral cavity during speech as well as during singing, whistling, blowing, sucking, swallowing, gagging, and vomiting. The valve then opens for nasal breathing and production of nasal sounds. As such, the velopharyngeal valve regulates and directs the transmission of sound energy and airflow in the oral and nasal cavities. In looking at the entire velopharyngeal mechanism, it is important to recognize that this is a three- dimensional tube that includes the anterior–posterior dimension, the vertical dimension, and the horizontal dimension. During closure, there must be coordinated movement of all structures in all dimensions so that the velopharyngeal valve can achieve closure like a sphincter.
The velopharyngeal sphincter requires the coordinated action of several different muscles, all of which are paired one muscle on each side of the midline. However, control of the velopharyngeal valve is very complex, requiring the interaction not only of these muscles but also of the articulators, particularly the tongue. Therefore, much more remains to be learned about the dynamics of the muscles and their interactions during speech.
The velopharyngeal port is bounded anteriorly by the soft palate (velum), laterally by the lateral pharyngeal walls and posteriorly by the posterior pharyngeal wall. Closure of the velopharynx during speech is a voluntary action that is mediated by the motor cortex and that requires the coordinated action of the velopharyngeal musculature.Velopharyngeal closure is critical for production of vowels and oral consonants so, has a profound impact on speech intelligibility.
Velopharyngeal closure between individuals, and even within an individual, is not always the same. Each individual has a certain basic pattern of closure that is dependent on the relative contributions of the muscles within the component structures. Despite this basic pattern, the height, strength, and timing of closure vary with the type of activity. For example, closure is much higher and firmer with nonpneumatic activities (i.e., vomiting) when compared to speech. More subtle varia- tions in closure are found during speech production, based on the type of phoneme produced, the phonemic context, and the rate of speech.
Velopharyngeal insufficiency (VPI) is the incomplete closure of the velopharyngeal port during speech production resulting in hypernasal speech, nasal air emission, compensatory misarticulating, decreased vocal intensity and facial grimacing.