Palate Anatomy
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.
Soft
palate
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.
Muscles
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.
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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.
