The roof of the mouth is called Palate (L. palate = roof of the mouth). The partition between the nasal and oral cavities is created by it.
The palate includes 2 parts,
- Hard palate, which creates the anterior 4-fifth of the palate and
- Soft palate, which creates the posterior one fifth of the palate.
Its anterior two-third is composed by the palatine processes of the maxillae and posterior one-third by the horizontal plates of the palatine bones. The hard palate is a partition between the nasal and oral cavities.
The superior and inferior surfaces of the hard palate create the floor of the nasal cavity and the roof of the oral cavity, respectively.
Anterolaterally, the hard palate becomes constant with the alveolar arches and gums.
The posterior margin of the hard palate is free and gives connection to the soft palate.
The inferior surface of the hard palate presents these features:
Incisive fossa, a small pit anteriorly in the midline supporting the incisor teeth, into which open the incisive canals. Every incisive canal/foramen (left and right) pierces the corresponding side and ascend into the corresponding nasal cavity. The incisive foramen conducts terminal parts of the nasopalatine nerve and greater palatine vessels.
Greater palatine foramen, 1 on every side, is located in the posterolateral corner of the hard palate medial to the final molar tooth. It carries the greater palatine nerve and vessels.
Lesser palatine foramina (1-3 in number) on every side are in the pyramidal process of palatine bone and are found just behind the greater palatine foramen. They offer passage to lesser palatine nerve and vessels.
Posterior nasal spine is a conical projection in the median plane on the sharp free posterior border of the hard palate.
Palatine crest is a curved ridge near the posterior border of the hard palate.
Masticatory mucosa is the mucous membrane lining the hard palate. In the anterior part, it’s steadfastly united with the periosteum by multiple fibrous strands (Sharpey’s fibres), for this reason moving bolus of food doesn’t displace the mucous membrane. It presents:
- transverse masticatory ridges on each side of mid-line and
- palatine raphe, a narrow ridge of mucous membrane going anteroposteriorly in the midline from a little papilla overlying the incisive fossa.
The hard palate is lined by keratinized stratified squamous epithelium.
This is by greater palatine arteries from the 3rd part of the maxillary artery. Every artery appears from greater palatine foramen and enters forwards around the palate (lateral to the nerve) to goes into the incisive canal and pass up into the nose.
The veins of hard palate drain into the pterygoid venous plexus (primarily) and pharyngeal venous plexus.
The hard palate is supplied by greater palatine and nasopalatine nerves originated from pterygopalatine ganglion. The greater palatine Nerve Supplies whole of the palate with the exception of anterior part of palate behind incisor teeth (the area of premaxilla) that is supplied by nasopalatine nerves.
The lymphatics from palate drain largely into the upper deep cervical lymph nodes and few into retropharyngeal lymph nodes.
The soft palate presents the following external features:
- Anterior (oral) surface is concave and marked by a median raphe.
- Posterior surface is convex and continuous with the floor of the nasal cavity.
- Superior border is connected to the posterior border of the hard palate.
- Inferior border is free and creates the anterior boundary of the pharyngeal isthmus. A conical, small, tongue like projection hanging down from its middle is referred to as uvula.
On every side from the base of uvula, 2 curved folds of mucous membrane stretch laterally and downwards:
- The anterior fold unites inferiorly with the side of the tongue (at the junction of oral and pharyngeal parts) and is called palatoglossal fold. The palatoglossal fold includes the palatoglossus muscle and creates the lateral boundary of the oropharyngeal isthmus.
- The posterior fold unites inferiorly with the lateral wall of the pharynx and is called palatopharyngeal fold. The palatopharyngeal fold includes palatopharyngeus muscle and creates the posterior boundary of the tonsillar fossa.
The soft palate is created from a fold of mucous membrane enclosing 5 pairs of muscles. The nasal surface of the soft palate is covered by pseudostratified ciliated columnar epithelium with the exception of posteriorly (the part that abuts on the Passavant’s ridge of posterior pharyngeal wall) that is lined by non-keratinized stratified squamous epithelium. The oral surface of the soft palate is thicker and lined by non-keratinized stratified squamous epithelium.
In the submucosa on both the surfaces are mucous glands, which are in loads around the uvula and on the oral aspect of the soft palate. The mucosa on the oral surface of the softpalate also includes some taste buds (particularly in children) and lymphoid follicles.
The soft palate is composed of the 5 pair of muscles, viz
- Tensor palati (tensor veli palatini).
- Levator palati (levator veli palatini).
- Musculus uvulae.
All the muscles of soft palate are extrinsic with the exception of musculus uvulae that are intrinsic.
Origin, Insertion and Activities of Muscle of The Soft Palate
- Separates the oropharynx from nasopharynx during swallowing so that food will not go into the nose.
- Sequester the oral cavity from oropharynx during mastication so that breathing isn’t changed.
- Helps to change the attribute of voice, by altering the level of blockage of the pharyngeal isthmus.
- Shields the damage of nasal mucosa during sneezing, by suitably breaking up and directing the gust of air via both nasal and oral cavities.
- Prevents the entrance of sputum into nose during coughing by directing it in the oral cavity.
Paralysis of soft palate: The paralysis of the muscles of soft palate (because of lesion of vagus nerve) creates:
- nasal regurgitation of liquids,
- nasal twang in voice,
- flattening of the palatal arch on the side of the lesion and
- deviation of uvula, opposite to the side of the lesion.
The soft palate is supplied by the following arteries:
- Lesser palatine branches of the maxillary artery.
- Ascending palatine branch of the facial artery.
- Palatine branches of the ascending pharyngeal artery.
The venous blood from palate is drained into pharyngeal venous plexus and pterygoid venous plexus.
The lymphatics from soft palate drain into retropharyngeal and upper deep cervical lymph nodes.
- All the muscles of soft palate are supplied by the cranial root of accessory nerve via pharyngeal plexus with the exception of tensor palati, which is supplied by the nerve to medial pterygoid, a branch of the mandibular nerve.
Sensory Supply: General sensations from palate are carried by:
- Lesser palatine nerves to the maxillary division of trigeminal nerve via pterygopalatine ganglion.
- Glossopharyngeal nerve.
Gag reflex: It’s a protective reflex defined by the elevation of the palate and contraction of the pharyngeal muscles with related retching and gagging in response to stimulant of the mucous membrane of the oropharynx. It takes place when the palate, tonsil, posterior part of the tongue, or posterior pharyngeal wall are contacted by unknown things like swab, spatula, etc. The afferent limb of the reflex is supplied by the glossopharyngeal nerve and efferent limb by the vagus nerve.
Development of the Palate
The face grows from 5 processes, which surround the archaic mouth or stomatodeum. The processes are as follows:
- Frontonasal process a single process.
- Maxillary processes (2) 1 on every side.
- Mandibular processes (2) 1 on every side.
The primary palate (also referred to as premaxilla) develops from the frontonasal process. The secondary palate grows from the palatine process of the maxillary processes.
2 palatine processes (1 on every side) grow from the inner aspects of the maxillary processes and fuse in the midline to create the secondary palate, which is shortly joined by nasal septum.
The hard palate is composed by the fusion of the secondary palate together with the primary palate. The incisive foramina indicate the junction of the 2 elements of the palate. The fusion happens from anterior to posterior parts.
The soft palate grows from 2 folds that develop posteriorly from the posterior border of the palatal processes. Consequently uvula is the last structure to grow. The 2 folds unify to create the soft palate.
The flawed fusion of different parts of the palate supplies rise to clefts in the palate. These vary greatly in amount, resulting in assortments of cleft palate, specifically whole cleft.
Unilateral entire cleft happens if maxillary process on 1 side doesn’t fuse with the premaxilla. It’s consistently connected with the cleft lip.
Bilateral entire cleft happens if both the maxillary processes don’t fuse with the premaxilla. In this type, secondary palate is split into 2 identical halves by a median cleft with an anterior V shaped cleft dividing the premaxilla entirely.
Incomplete or partial cleft: The subsequent periods may take place
- Bifid uvula-cleft affecting only uvula. It’s of no clinical relevance.
- Cleft of soft palate-affecting uvula and soft palate.
- Cleft of soft palate-extending into the hard palate.