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Oral cavity

The oral cavity, also known as the mouth’s cavity (Latin: cavitas oris), is the digestive tract’s initial part. It is located anteriorly in the lower part of the face and head right under the nasal cavity. The oral cavity starts the digestion process, and it is the entrance to the digestive system. It also has an essential role in speech formation and respiration processes. It consists of multiple anatomical structures that efficiently provide the oral cavity functions and normal physiological processes.

Oral cavity anatomy

Although the oral cavity is a small anatomical structure in the human body, it is a significant part of the digestive system. It has two divisions, four walls, and two openings. The oral cavity’s anatomical structures include lips, cheeks, gums, teeth, the tongue, soft and hard palate, and three salivary gland pairs.

 Parts of the oral cavity 

The oral cavity anatomically consists of two main parts. The anterior region is called the oral vestibule, but the posterior part - the oral cavity proper - both are separated by the alveolar arches of the mandible and maxilla, gingiva, and teeth. The oral cavity proper and oral vestibule connects through the gap between teeth if the mouth is open. But if the teeth are closed, the connection is provided by an aperture behind the last molar teeth.

Oral vestibule

The oral vestibule is the horseshoe-like shaped area bounded externally by the lips and cheeks and internally by the teeth and gingiva and the inner aspect of the cheeks. It connects the external environment with the oral cavity proper.

Oral cavity proper

The oral cavity proper is the area behind the teeth. The oral cavity proper extends from the maxilla’s and mandible’s alveolar arches to the entry into the oral part of the pharynx (oropharynx) posteriorly. The oral cavity proper contains the tonguesoft and hard palate, and three pairs of salivary glands such as parotid, sublingual and submandibular glands. The tongue fills the oral cavity proper.

Walls of the oral cavity 

The oral cavity anatomy includes four walls - the roof, two lateral walls, and a floor, and two openings - anterior and posterior. The maxilla, mandible, palatine bone, and the hyoid bone, also part of the sphenoid and temporal bones, form the oral cavity’s anatomical bone frame.

Anatomy of the walls

The roof or superior wall form the hard palate anteriorly and the soft palate posteriorly. It separates the nasal cavity from the oral cavity.

The mucous membrane and soft tissue of the cheeks and the mastication and facial muscles, mostly buccinator, form the inside of the lateral walls. Mylohyoid and geniohyoid muscles build the floor of the mouth or the inferior part of the oral cavity. In the floor part also lie the sublingual and submandibular salivary glands. 

Openings of the oral cavity 

Anteriorly, the cavity of the mouth begins at the border between the facial skin and lips. It opens through the oral fissure that connects the outside of the body with the oral cavity’s anterior part - the oral vestibule. Several muscles control the oral fissure’s movements, such as the orbicularis oris, the depressors and elevators of the lips, the zygomaticus major and minor. Also the risorius, and buccinator muscles take part in providing motions. The posterior opening connects the oral cavity proper with the beginning of the pharynx, known as the oropharynx. The junction between the oral cavity and pharynx is called the oropharyngeal isthmus or the oropharyngeal opening, also the isthmus of the fauces. To sum up, uvula, palatine and lingual tonsils, the tongue’s root, palatopharyngeal arch form the posterior opening of the oral cavity.

Mucous membrane 

The surfaces of the oral cavity are mostly lined by a mucous membrane - the oral mucosa. It consists of two layers - the external layer is the epithelium, but under it lies lamina propria, a thin layer made by loose connective tissue. Both layers together form a thick mucosa. Apart from the skin, the oral cavity surfaces are mostly lined by the stratified squamous and non-keratinized epithelium. The mucosal part of lips and cheeks, soft palate (oral cavity part), floor of the oral cavity, and the tongue’s ventral surface have a non-keratinized epithelium. The hard palate (oral cavity part), gums, most of the tongue’s dorsal surface, and the outer part of the lips have ortho- (entirely) or parakeratinized (partially, incomplete keratinized) epithelium. Apart from other anatomical structures covered with stratified squamous epithelium, the teeth have decalcified tissue.

Oral cavity functions

In general, there are three functions provided by the oral cavity. It helps to accomplish digestionrespiration, and the formation of speech.

Digestion 

The primary oral cavity function is digestion. After the individual has seen or smelt the food, salivary glands start to produce saliva that helps with the food processing, hydration, and lubrication. In the oral cavity, two different types of food processing take place. One of the oral cavity functions is the mechanical food procession that mainly provides the teeth as they help to chew the food into smaller particles and pieces. Another function of the oral cavity is the chemical food procession in which the salivary gland produced saliva has a central role. It contains an enzyme called amylase that starts to digest carbohydrates already in the mouth. To be more precise, amylase starts to break down and hydrolyze starch, which is found in many products, into smaller molecules. The tongue that occupies the oral cavity has an essential role in digestion as well. It helps to form bolus from chewed food by pressing it against the palates and moves it to the pharynx. The tongue helps to taste the food by the lingual papillae, located in the dorsal surface.

Speech formation and respiration

Apart from the primary oral cavity function, there are two more essential roles. The oral cavity provides the modification of the sound produced in the larynx and speech formation. The lips, soft and hard palate, teeth, and tongue are articulators located in the oral cavity. All these structures help to resonate voice and support word-formation. Together with the nasal cavity, the oral cavity provides the air passage from the outside environment to the lower respiratory system organs. It is involved in the respiration process.

Most common diseases 

As in other anatomical structures, there is a wide range of different conditions causing abnormal oral cavity functioning and oral cavity anatomical changes. If left untreated, oral diseases can have a substantial negative and even life-threatening impact on other organ systems. For example, many teeth problems can lead to serious heart issues as poor dental health and hygiene can increase the risk of infections that can get into the bloodstream causing bacterial endocarditis, an inflammation in the heart tissue lining the heart chambers that commonly occurs in one or more valves.

As the oral cavity is visible to others, it can affect individuals’ physical health and significantly impact mental health. Most conditions in the oral cavity can be easily preventable and treatable unless diagnosed and treated early. 

Risk factors 

The most common risk factors causing a wide range of different conditions are:

  • poor and unhealthy diet rich in sugars and fast food,
  • use of tobacco and alcohol,
  • poor hygiene,
  • obesity,
  • low social status,
  • genetic predisposition,
  • age,
  • stress,
  • medications reducing the amount of produced saliva,
  • clenching or grinding the teeth,
  • presence of chronic and systemic diseases such as diabetes.

Lifelong conditions 

The most common conditions are dental caries or tooth decay or dental cavities, periodontal disease (gum disease), infectious diseases such as HIV manifestations in the mouth or oral herpes, various injury traumas, and oral cancers. Oral cancers are among the most common cancers, affecting any part of the oral cavity. Mostly they are found in older people and men.

Genetic disorders 

Although genetic disorders are not as common as lifelong diseases, various oral manifestations of genetic diseases are common. Cleft palate and cleft lip are among the most common oral presentations and congenital disabilities associated with inherited genetic disorders. It happens when anatomical structures of the face develop in an unborn baby and don’t completely close. For example, Down syndrome can present with it.

Summary on the oral cavity 

What is the oral cavity? 

The oral cavity is the very first anatomical part of the digestive system. It starts with the lips and ends with the hard palate, where the pharynx, the next part of the alimentary system, starts. The connection place is called the oropharyngeal isthmus.

What does the oral cavity contain? 

The oral cavity anatomy forms lips, gums, cheeks, teeth, soft and hard palate, the tongue, and three pairs of salivary glands - sublingual, submandibular, and parotid.

What are the parts of the oral cavity?

The oral cavity anatomy has two main parts - the oral vestibule and the oral cavity proper.

What is the difference between the vestibule and the oral cavity? 

The vestibule is the oral cavity entrance, while the oral cavity proper is the central part where mainly all the processes occur.

What is the floor of the mouth called?

The floor of the mouth is also called the inferior wall of the oral cavity. And it is the part that locates beneath the tongue between the sides of the mandible.

What forms the roof of the mouth? 

The roof of the mouth is formed by the soft palate anteriorly and hard palate posteriorly.

What type of tissue covers the oral cavity? 

Mucous membrane or oral mucosa covers the oral cavity.

What are the three types of oral mucosa? 

The oral mucosa classifies into three categories. Mainly the stratified squamous and non-keratinized epithelium lines the oral mucosa. Two other types are the stratified squamous fully or partially keratinized epithelium and the decalcified. The teeth have it.

What happens in the oral cavity? 

There are three oral cavity functions. It helps to provide digestion, respiration, and the formation of speech.

What is the primary oral cavity function? 

The primary oral cavity function is the mechanical and chemical food procession, so the structure plays an essential part in the digestion process.

What causes diseases in the oral cavity?

The most common causes include unhealthy diet, overuse and frequent consumption of tobacco and alcohol, poor mouth hygiene, certain infections, and poorly controlled chronic diseases such as diabetes.

What are the most common diseases in the oral cavity? 

The most common conditions are dental caries, periodontal disease, infectious diseases, various injury traumas, and oral cancers.