The oral cavity, better known as the mouth, is the start of the alimentary canal. It has three major functions:
- Digestion – receives food, preparing it for digestion in the stomach and small intestine.
- Communication – modifies the sound produced in the larynx to create a range of sounds.
- Breathing – acts as an air inlet in addition to the nasal cavity.
In this article, we shall look at the anatomy of the oral cavity – its divisions, contents, and any clinical correlations.
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Divisions of the Oral Cavity
The oral cavity spans between the oral fissure (anteriorly – the opening between the lips), and the oropharyngeal isthmus (posteriorly – the opening of the oropharynx).
It is divided into two parts by the upper and lower dental arches (formed by the teeth and their bony scaffolding). The two divisions of the oral cavity are the vestibule and the mouth cavity proper.
Vestibule
The horseshoe-shaped vestibule is situated anteriorly. It is the space between the lips/cheeks, and the gums/teeth.
The vestibule communicates with the mouth proper via the space behind the third molar tooth, and with the exterior through the oral fissure. The diameter of the oral fissure is controlled by the muscles of facial expression – principally theorbicularis oris.
Opposite the upper second molar tooth, the duct of the parotid gland opens out into the vestibule, secreting salivatory juices.
Fig 1
The two divisions of the oral cavity are the vestibule and oral cavity proper.
Mouth Proper
The mouth proper lies posteriorly to the vestibule. It is bordered by a roof, a floor, and the cheeks. The tongue fills a large proportion of the cavity of the mouth proper.
Roof
The roof of the mouth proper consists of the hard and soft palates.
The hard palateis found anteriorly. It is a bony plate thatseparates the nasal cavity from the oral cavity. It is covered superiorly by respiratorymucosa (ciliated pseudostratified columnar epithelium) and inferiorly by oral mucosa (stratified squamous epithelium).
The soft palateis a posterior continuation of the hard palate. In contrast to the hard palate, it is a muscular structure. It acts as a valve that can lower to close the oropharyngeal isthmus, and elevate toseparate the nasopharynx from the oropharynx.
Cheeks
The cheeks are formed by the buccinator muscle, which is lined internally by the oral mucous membrane.
The buccinator muscle contracts to keep food between the teeth when chewing, and is innervated by the buccal branches of the facial nerve (CN VII).
Floor
The floor of the oral cavity consists of several structures:
- Muscular diaphragm –comprised of the bilateral mylohyoid muscles. It provides structural support to the floor of the mouth, and pulls the larynx forward during swallowing.
- Geniohyoid muscles – pull the larynx forward during swallowing.
- Tongue – connected to the floor by the frenulum of the tongue, a fold of oral mucosa.
- Salivary glands and ducts.
Fig 2
Structures of the oral cavity floor.
Innervation
Sensory innervation of the oral cavity is supplied by the branches of the trigeminal nerve (CN V).
The hard palate is innervated by thegreater palatineandnasopalatine nerves,both of which are branches of the maxillary nerve (CN V2). The soft palate is innervated bylesser palatine nerve, another branch of the maxillary nerve.
The floor of the oral cavity receives sensory innervation from the lingual nerve – a branch of the mandibular (V3) division of the trigeminal nerve. The tongue is also innervated by special sensory fibres for taste from the chorda tympani, a branch of the facial nerve (CN VII).
The cheeks are innervated by the buccal nerve. It is also a branch of the mandibular division of the trigeminal nerve (not to be confused with the buccal branches of the facial nerve).
Fig 3
The lingual nerve provides sensory innervation to the tongue.
Clinical Relevance
The Gag Reflex
The gag reflex is protective against foreign bodies touching the posterior aspects of the oral cavity, which are most innervated by theglossopharyngeal nerve(CN IX).
When stimulated, a reflex arc leads to contraction of the pharyngeal musculature and the elevation of the soft palate. The efferent nerve in this case is the vagus nerve (CN X).
FAQs
The innervation of the oral cavity is distinct and comes primarily from the maxillary and mandibular divisions of the trigeminal nerve. The oral mucosa, teeth, and supporting structures receive their innervation from the maxillary and mandibular divisions of the trigeminal nerve.
What are the divisions of the oral cavity? ›
The oral cavity spans between the oral fissure (anteriorly – the opening between the lips), and the oropharyngeal isthmus (posteriorly – the opening of the oropharynx). It is divided into two parts by the upper and lower dental arches (formed by the teeth and their bony scaffolding).
Which cranial nerves numbers that innervate the oral cavity? ›
When discussing the function of the oral cavity, probably the most important nerve is the trigeminal. The trigeminal nerve or fifth CN is the largest of the CNs and is the major sensory nerve of the face and scalp.
How many nerves are in the oral cavity? ›
The nerves of the oral cavity include the trigeminal nerve (CN V), facial nerve (CN VII), glossopharyngeal nerve (CN IX), vagus nerve (CN X), and hypoglossal nerve (CN XII).
What nerve Innervates the teeth ____? ›
Trigeminal nerve (V): A mixed nerve. The sensory fibers of this nerve carry impulses for general sensation (touch, temperature and pain) associated with the face, teeth, lips and eyelids. The motor fibers of this nerve carry impulses to some of the mastication muscles of the face.
What Innervates the nerves in the teeth? ›
The innervation and blood supply of the maxillary and mandibular teeth are dependant on the blood vessels and nerves that supply the upper and lower jaws. As the maxilla is deemed part of the midface and the mandible part of the lower face respectively, it is logical to assume that they have separate neurovasculature.
What are the cavity divisions? ›
The ventral cavity is subdivided into the thoracic and abdominopelvic cavities.
- The thoracic cavity fills the chest and is subdivided into two pleural cavities and the pericardial cavity. ...
- The abdominopelvic cavity fills the lower half of the trunk and is subdivided into the abdominal cavity and the pelvic cavity.
The oral cavity includes the lips, hard palate (the bony front portion of the roof of the mouth), soft palate (the muscular back portion of the roof of the mouth), retromolar trigone (the area behind the wisdom teeth), front two-thirds of the tongue, gingiva (gums), buccal mucosa (the inner lining of the lips and ...
How are the quadrants of the oral cavity divided? ›
Quadrant 1 (top right) Quadrant 2 (top left) Quadrant 3 (bottom left) Quadrant 4 (down on your right)
Which cranial nerves innervate? ›
| Muscles Innervated by Cranial Nerves |
|---|
| Cranial Nerve | Muscle |
|---|
| Abducens nerve (CN VI) | Lateral rectus |
| Facial nerve (CN VII) | Muscles of facial expression Posterior belly of digastric muscle Stylohyoid muscle Stapedius muscle |
| Glossopharyngeal nerve (CN IX) | Stylopharyngeus muscle |
6 more rowsApr 9, 2020
Maxillary Primary Teeth - The maxillary teeth are innervated by the: Superior alveolar nerve branch of the maxillary nerve[9] Anterior and middle superior alveolar nerve branches of the infraorbital nerve.
What is the somatosensory innervation of the oral cavity? ›
The oral somatosensory system relays essential information about mechanical stimuli to enable oral functions such as feeding and speech. The neurochemical and anatomical diversity of sensory neurons across oral cavity sites have not been systematically compared.
What is the main nerve in the mouth? ›
The lingual nerve is a sensory nerve that arises from the mandibular division of the trigeminal nerve (cranial nerve V). The lingual nerve is often in a common stem with the inferior alveolar nerve after the mandibular division enters the infratemporal fossa through the foramen ovale [1].
Which is a major function of the oral cavity? ›
The two main functions of the mouth are eating and speaking. Parts of the mouth include the lips, vestibule, mouth cavity, gums, teeth, hard and soft palate, tongue and salivary glands. The mouth is also known as the oral cavity or the buccal cavity.
What cranial nerve allows you to cry? ›
The facial nerve is the 7th cranial nerve and carries nerve fibers that control facial movement and expression. The facial nerve also carries nerves that are involved in taste to the anterior 2/3 of the tongue and producing tears (lacrimal gland).
What is the innervation of Orodental tissues? ›
Innervation of orodental tissues. Excepting regions around the oropharyngeal isthmus, the sensory innervation of the oral mucosa is derived from the maxillary and mandibular divisions of the trigeminal nerve. The trigeminal nerve also supplies the teeth and their supporting tissues (see Table 6.1).
What Innervates the floor of the mouth? ›
The lingual nerve lies anterior to the inferior alveolar nerve and provides sensory innervation to the floor of the mouth and the lingual gingiva.
