Structure
The hard palate is located on the roof of the oral cavity, posterior and medial to the alveolar process of the maxilla. The bony structure is formed by the palatine processes of the maxilla and the horizontal plates of the palatine bones. The periosteum is covered by a firmly attached mucosa centrally, although a submucosa is apparent laterally containing vessels. The hard palate is continuous with the soft palate posteriorly.
Relations
Superiorly with the nasal cavity and maxillary sinus
Inferiorly with the oral cavity
Laterally with the alveolar process of the maxilla, the gingiva and teeth
Macroscopic Features
The hard palate is typically a pale pink colour and may have an orange peel appearance from the palatine salivary glands (more common posteriorly). The incisive papilla is located just posterior to the central incisors and is just posterior to the incisive foramen (for the nasopalatine nerve / vessels). Extending posteriorly to this papilla is the palatine raphe, a pale streak which marks the fusion of the embryonic palatal processes. Transverse palatine folds extend laterally from the incisive papilla and assist in manoeuvring food.
Microscopic Features
The hard palate is lined with a keratinising stratified squamous epithelium, tightly bound to the underlying periosteum of the palatine bone/maxilla. There is minimal submucosa, which becomes more prominent posteriorly.
Pathological Variations
Cleft palate occurs when the palatine shelves fail to fuse. It may be mild (cleft uvula or soft palate) or major, leading to a defect between the oral cavity and the nasal cavity.
Neurovascular Supply
Arterial Supply
The greater palatine artery is the larger branch of the descending palatine artery of the maxillary artery. It enters the palate through the greater palatine foramen (medial to the 3rd molar) and runs anteromedially towards the incisive foramen. Unlike the nerve, it ascends through the incisive foramen and anastamoses with branches of the nasopalatine artery.
Venous Drainage
Veins from the hard palate terminate in the pterygoid venous plexus.
Lymphatics
Lymph vessels may pass to submandibular (IB) or superior deep cervical nodes (level II). Retropharyngeal nodes are very rarely involved.
Innervation
The hard palate is innervated by branches of the maxillary nerve, both of which initially pass through the pterygopalatine ganglion. The greater palatine nerve descends through the greater palatine foramen with its companion artery, and runs anteromedially to supply the mucosa of the posterior hard palate. The nasopalatine nerve descends through the incisive foramen to supply the most anterior parts of the hard palate.
Afferent fibres from taste buds are thought to travel with the greater palatine nerve to the pterygopalatine ganglion, where they leave with the nerve of the pterygoid canal and continue with the greater petrosal nerve to the facial ganglion. Secretomotor fibres to the salivary glands on the posterior hard palate have their cell bodies in the pterygopalatine ganglion and travel to the hard palate with the greater palatine nerve.
Routes of Cancer Spread
Local Invasion
Tumours of the palate may invade into the surrounding gingivae and alveolar process of the maxilla, superiorly through the palatine bone into the nasal cavity, or posteriorly into the soft palate. Extension posterolaterally into the pterygopalatine fossa may also occur.
Lymphatic Spread
The lymphatics of the palate generally drain to submandibular nodes or directly to superior deep cervical nodes (level 2). Midline regions may drain bilaterally. Retropharyngeal nodes may rarely be involved.
Neurological Spread
Tumours of the hard palate may follow nerves back to the pterygopalatine plexus and onwards to the maxillary nerve.
Haemotogenous Spread
Like most head and neck SCC, haemotogenous spread usually occurs to the lungs, bone and liver.
