The palate consists of hard and soft parts covered by mucous membrane (Fig. 7.55). The hard palate separates the oral and nasal cavities while posteriorly the soft palate separates the nasopharynx from the oropharynx.
The bones that comprise the hard palate are the palatine processes of the maxillae anteriorly and the horizontal plates of the palatine bones posteriorly (Fig. 7.82). The hard palate is bounded in front and laterally by the superior alveolar ridge. The soft palate is attached to the free posterior border of the hard palate. Sensory fibres reach the palate in branches of the maxillary (V2) division of the trigeminal nerve. The nasopalatine nerve emerges from the incisive foramen and supplies the anterior part of the hard palate. The greater palatine nerve gains the hard palate via the greater palatine foramen and innervates its posterior portion.
The soft palate projects into the cavity of the pharynx from its attachment to the posterior edge of the hard palate. When elevated, it separates the oropharynx from the nasopharynx. Five paired muscles attach to the soft palate and contribute to its structure. In the midline the uvula projects downwards from its posterior free border.
Tensor veli palatini (Fig. 7.57) attaches to the scaphoid fossa and spine of the sphenoid and to the lateral surface of the cartilaginous portion of the auditory (Eustachian) tube. Its fibres descend between the lateral and medial pterygoid plates on the lateral aspect of the pharyngeal wall and give way to a tendon just above the pterygoid hamulus. The tendon hooks under the hamulus and turns medially to enter the soft palate, where it forms the palatine aponeurosis by fanning out and attaching to the posterior border of the hard palate. The palatine aponeurosis forms the basic structure of the soft palate to which other muscles gain attachment. Tensor veli palatini is supplied by the mandibular (V3) division of the trigeminal nerve and tenses the soft palate.
Levator veli palatini (Figs 7.56 & 7.57) attaches to the inferior surface of the petrous temporal bone just medial to the opening of the auditory tube and to the adjacent part of the tube. Its fibres descend medial to the medial pterygoid plate within the pharynx and attach to the upper surface of the palatine aponeurosis. The muscle is innervated by the pharyngeal plexus (p. 364). Levator veli palatini elevates the soft palate during swallowing, preventing regurgitation of food into the nasal cavities.
Palatoglossus (Fig. 7.56) descends from the inferior surface of the palatine aponeurosis and inclines slightly forwards to enter the posterolateral part of the tongue. The position of palatoglossus is evident on the inner surface of the oral cavity as a mucosal elevation, the palatoglossal ridge (anterior pillar of the fauces; Fig. 7.55). The two palatoglossal ridges form the oropharyngeal isthmus, which marks the posterior boundary of the oral cavity. Innervated by fibres from the pharyngeal plexus, palatoglossus lowers the soft palate, raises the posterior part of the tongue and moves the pala- toglossal ridge towards the midline, thus narrowing the isthmus.
Palatopharyngeus (Figs 7.56 & 7.57) attaches to the undersurface of the soft palate. Most of its fibres run posteroinferiorly as part of the longitudinal layer of muscle inside the pharynx and form the palatopharyngeal ridge (posterior pillar of the fauces). On contraction, these fibres depress the soft palate. Other fibres pass horizontally backwards, raising the mucosa into a ridge, against which the soft palate is elevated. Palatopharyngeus receives its motor supply from the pharyngeal plexus.
The uvular muscle (Figs 7.56 & 7.57), also supplied by the pharyngeal plexus, lies entirely within the soft palate and elevates the uvula. In cases of unilateral paralysis of the soft palate, the uvula rises asymmetrically, being pulled away from the paralysed side.
Sensory and secretomotor innervation to the soft palate is from the lesser palatine nerves of the maxillary (V2) division of the trigeminal nerve, supplemented laterally on the undersurface of the palate by the glossopharyngeal (IX) nerve.
Fig. 7.57 Posterior view of soft palate after removal of cervical vertebral column and posterior wall of pharynx. On the left side, the medial pterygoid and the mucosa of the soft palate have been removed to reveal the muscles.