If the hyoid is fixated, these muscles lower the mandible and also assist in the retrusion of mandible. The graviational force rather than muscle action is primarily responsible for lowering the mandible. There are 20 deciduous and 32 permanent teeth as shown in the figure below. These teeth erupt between 6 months and 2 years and are normally shed between six and 12 years of age. They erupt between six and 17 years.
Malocclusion refers to the alignment of upper and lower teeth.
The opening between the oropharynx below and the nasopharynx above is called the velopharyngeal port . The port is normally open except during deglutition and the production of nonnasal sounds. Their contraction also opens the Eustachian tube. The paired lavator palatini muscle, originating from the medial pterygoid plate and inserting into the palatine aponeurosis, pulls the velum up and back towards the posterior pharyngeal wall. This action closes off the velopharyngeal port.