The oral cavity, better known and referred to most commonly as the mouth, is the starting point of the alimentary canal. It carries out three major functions- digestion, communication, and breathing. In the process of digestion it receives food, breaking it down and preparing it for further digestion in the stomach and small intestine. For communication, the mouth modifies the sound produced in the larynx to create a range of sounds. As for breathing, it acts as an air inlet in addition to the nasal cavity. In this article, we shall take a closer look at the anatomy of the oral cavity- its divisions, contents, and any clinical correlations.
The oral cavity stretches between the oral fissure, which is the opening between the lips at the anterior point, and the oropharyngeal isthmus, the opening of the oropharynx at the posterior point. It is split into two parts by the upper and lower dental arches, which are formed by the teeth and their bony scaffolding.
The two divisions of the oral cavity are the vestibule and the mouth cavity proper.
The vestibule is located at the anterior end and is shaped like a horseshoe. It is the space between the lips and cheeks, and the gums and teeth. The vestibule communicates with the mouth proper through the space behind the third molar tooth, and with the exterior through the oral fissure. The diameter of the oral fissure is managed by the muscles of facial expression, mainly the orbicularis oris. At the opposite of the upper second molar tooth, the duct of the parotid gland opens out into the vestibule and secretes salivatory juices.
The mouth proper is situated posteriorly to the vestibule. It is bordered by a roof, a floor, and the cheeks. The tongue takes up a good proportion of the space in the mouth proper.
The roof of the mouth proper is composed of the hard and soft palates. The hard palate is located at the front. It is a bony plate which separates the nasal cavity from the oral cavity. It is covered superily by respiratory mucosa, which is ciliated pseudostratified columnar epithelium, and inferiorly by oral mucosa, which is stratified squamous epithelium. The soft palate is the posterior extension of the hard palate. In contrast to the hard palate, it is a muscular structure and serves as a valve. It lowers to close the oropharyngeal isthmus and elevates to separate the nasopharynx from the oropharynx.
The cheeks are comprised of 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).
The floor of the oral cavity comprises several components. These include the muscular diaphragm, which is composed of the bilateral mylohyoid muscles, the geniohyoid muscles, the tongue, which is connected to the floor by the frenulum of the tongue, a fold of oral mucosa, as well as salivary glands and ducts.
Sensory innervation of the oral cavity is supplied by the branches of the trigeminal nerve (CN V). The hard palate is innervated by the greater palatine and nasopalatine nerves, both of which are branches of the maxillary nerve (CN V2). The soft palate is innervated by the lesser palatine nerve, which is another branch of the maxillary nerve. The floor of the oral cavity receives sensory innervation from the lingual nerve, which is 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, which is also a branch of the mandibular division of the trigeminal nerve (not to be confused with the buccal branches of the facial nerve).
The components and functions of the oral cavity are extremely important for the overall wellbeing of the body. The hard and soft palate help regulate airflow from the nose to the mouth and vice versa. They also aid in speech production. The buccinator muscle is instrumental in keeping food between the teeth when chewing, and the mylohyoid muscles, geniohyoid muscles, and frenulum of the tongue provide structural support to the floor of the mouth and help pull the larynx forward during swallowing.
The trigeminal nerve is responsible for the sensory nerve supply of the oral cavity, and the facial nerve provides sensory fibres for taste. The salivary glands and ducts are essential for lubricating the oral cavity and preparing food for digestion. All of these components must work together for proper digestion, communication, and other vital functions.
The oral cavity is a complex structure involved in a variety of essential physiological processes. Its proper functioning is vital for digestion, communication, and breathing. While the anatomy of the oral cavity is complex, understanding its components and functions can help us appreciate the importance of taking proper care of our body and how it works.
The oral cavity is divided into two distinct areas, the vestibule and the mouth proper. The vestibule is located in the anterior region and is horseshoe-shaped. It is located between the lips and cheeks, and the gums and teeth. It communicates with the mouth proper through the space located behind the third molar tooth, and with the exterior, through the oral fissure. The diameter of the oral fissure is regulated by the muscles of facial expression, mainly the orbicularis oris. On the opposite side of the upper second molar tooth lies the opening of the parotid gland, which secretes salivary juices into the vestibule.
The mouth proper lies posterior to the vestibule and has a roof, floor, and cheeks. The tongue takes up a significant portion of the cavity in the mouth proper.
The roof of the mouth is comprised of the hard and soft palate. The hard palate is located in the anterior region, and acts as a barrier between the nasal cavity and the oral cavity. It is covered superiorly by respiratory mucosa, composed of ciliated pseudostratified columnar epithelium, and inferiorly by oral mucosa, which contains stratified squamous epithelium. The soft palate is a posterior continuation of the hard palate and is composed of muscle. It serves as a valve that closes off the oropharyngeal isthmus when lowered, and separates the nasopharynx and oropharynx when raised.
The cheeks are formed by the buccinator muscle and are lined internally by the oral mucous membrane. The buccinator muscle contracts to keep food between the teeth when chewing, and its innervation is provided by the buccal branches of the facial nerve (CN VII).
The floor of the oral cavity contains several structures, including the muscular diaphragm and geniohyoid muscles, both of which help in providing structural support to the floor of the mouth. The diaphragm also pulls the larynx forward during swallowing. The floor of the oral cavity also includes the tongue, which is connected to the floor by the frenulum of the tongue, a fold of oral mucosa. Additionally, the floor of the oral cavity contains the salivary glands and ducts.
The sensory innervation of the oral cavity is supplied mainly by the branches of the trigeminal nerve (CN V). The hard palate is innervated by the greater palatine and nasopalatine nerves, both of which are branches of the maxillary nerve (CN V2). The soft palate is innervated by the lesser palatine nerve, another branch of the maxillary nerve. The floor of the oral cavity is innervated by the lingual nerve, a branch of the mandibular (V3) division of the trigeminal nerve, and the tongue is also innervated by special sensory fibres for taste that come from the chorda tympani, a branch of the facial nerve (CN VII). The cheeks are innervated by the buccal nerve, another branch of the mandibular division of the trigeminal nerve (not to be confused with the buccal branches of the facial nerve).
The lingual nerve provides sensory innervation to the tongue. This is of particular clinical relevance, as sensations from the posterior aspects of the oral cavity are mostly relayed by the glossopharyngeal nerve (CN IX). When stimulated, this nerve initiates a reflex arc that causes the pharyngeal musculature to contract and the soft palate to elevate. The efferent nerve in this case is the vagus nerve (CN X).
