cavity behave as a filter to remove particulate matter. These nasal turbinates further circulate the air around the nasal cavity to warm, filter and humidify the inspired air as it crosses the nasal epithelium. In the nasal cavity, inspired air exposes the olfactory nerves to various aromas from the environment. When airflow increases, breathing becomes oral in addition to nasal. If one was required to breathe at all times the upper airway would be rigid and permanently open. However, the secondary function of the upper airway is
deglutition and this requires the upper airway to be soft, distensible and collapsible thus
allowing the passage of solid and liquid foods while swallowing. The rˆole of the soft palate is to move posteriorly against the wall of the pharynx when a person swallows, thereby preventing regurgitation of food into the nasal cavity. Elevation and lowering of the soft palate can also regulate nasal and oral breathing. Other functions of the upper airway
are coughing and speech. Coughing protects the lungs from inhaling foreign objects and
clears secretions. The vocal sound known as speech is produced in the larynx within a pair of vocal cords. The larynx is situated in front of the neck above the trachea and is made up of a framework of nine pieces of cartilage bound together by ligaments and muscles lined with mucous membrane.
A.2
The Palate
This section aims to relate the complexity of such a seemingly simple part of the human anatomy. This description of the palate is adapted from Moore and Agur (1995) and Berger (1964). The palate, two views of which are shown in figure A.2, forms the roof of the mouth and the floor of the nasal cavities. The palate consists of two regions: the hard palate (the anterior two-thirds or bony part) and the soft palate (the posterior one-third or fibromuscular part). The hard palate is formed by the palatine process of the maxillae and the horizontal plates of the palatine bones. The incisive foramen is posterior to the central incisor teeth. The incisive canal transmits the nasopalatine nerve and the terminal branch of the sphenopalatine artery. Medial to the third molar tooth the greater palatine foramen pierces the lateral border of the bony palate. The greater
A.2 The Palate vi
(a) From Gray (1936).
(b) From Moore and Agur (1995).
A.2.1 Musculature vii
palatine vessels and nerve emerge from this foramen and run anteriorly on the palate. The lesser palatine foramina transmit the lesser palatine nerves and vessels to the soft palate and adjacent structures. The soft palate is the posterior fibromuscular part of the palate that is attached to the posterior edge of the hard palate. It extends posterioinferiorly as a curved free margin from which hangs a conical process, the uvula. Laterally the soft palate is continuous with the wall of the pharynx and is joined to the tongue and the pharynx by the palatoglossal and palatopharyngeal arches respectively. The palatine tonsils are two masses of lymphoid tissue, one on each side of the oropharynx. Each is in a tonsillar fossa, bounded by the palatoglossal and palatopharyngeal arches and the tongue. The soft palate is strengthened by the palatine aponeurosis formed by the expanded tendon of thetensor veli-palatini. The aponeurosis, attached to the posterior margin of the hard palate, is thick anteriorly and thin posteriorly. The anterior part of the soft palate is formed mainly by the aponeurosis, whereas the posterior part is muscular.
A.2.1
Musculature
Muscles of the soft palate arise from the base of the cranium and descend to the palate. The soft palate may be raised so that it is in contact with the posterior wall of the pharynx. The soft palate can also be drawn inferiorly so that it is in contact with the posterior part of the tongue. The muscles of the soft palate and their independent rˆoles are:
• Levator veli-palatini is a cylindrical muscle that runs inferoanteriorly, spreading
out in the soft palate where it attaches to the superior surface of the palatine aponeurosis. It elevates the soft palate during swallowing and yawning;
• Tensor veli-palatini is a triangular muscle that passes inferiorly; its tendon hooks
around the hamulus of the medial pterygoid plate before inserting into the palatine aponeurosis. It tenses the soft palate and opens the mouth auditory tube during swallowing and yawning;
A.2.2 Blood Supply viii
• Palatoglossus is a slender slip of muscle covered with mucous membrane and forms
the palatoglossal arch. It elevates the posterior part of the tongue and draws the soft palate onto the tongue;
• Palatopharyngeus is a thin flat muscle covered with mucous membrane and forms
the palatopharyngeal arch. It tenses the soft palate and pulls the walls of the pharynx superiorly, anteriorly and medially during swallowing;
• Musculus uvulae inserts into the mucosa of the uvula. It shortens the uvula and
pulls it superiorly.
A.2.2
Blood Supply
The palate has a rich blood supply chiefly from the greater palatine artery on each side, a branch of the descending palatine artery. This artery passes through the greater palatine foramen and runs anteriorly and medially. The lesser palatine artery enters through the lesser palatine foramen and anastomoses with the ascending palatine artery, a branch of the facial artery. The veins of the palate, corresponding and accompanying the branches of the maxillary artery, are tributaries of the pterygoid plexus.
A.2.3
Nervous System
The sensory nerves of the palate are branches of the pterygopalatine ganglion. The greater palatine nerve supplies the gingivae, mucous membrane and glands of most of the hard palate. The nasopalatine nerve supplies the mucous membrane of the anterior part of the hard palate. The lesser palatine nerve supplies the soft palate. The palatine nerves accompany the arteries through the greater and lesser palatine foramina respectively. Except for the tensor veli-palatini supplied by the nerve CN V2, all muscles of the soft