Updated 2nd of January 2022
The mouth, also called the oral cavity, is the opening by which food enters the body and where digestion begins. It is the first section of the digestive tract that receives food and produces saliva to mechanically break up solid particles into smaller pieces.
The content of the mouth determines all its functions, which in addition to eating, it serves in breathing and communicating.
Anatomy and structure
The mouth is located in front of the face, between the nose and the chin. Inside the head, it spans from the oral fissure (front opening of the mouth) to the oropharyngeal isthmus in the back, which communicates with the oropharynx.
There are two regions in the mouth, the vestibule, and the oral cavity proper. The vestibule is located to the front, and is the space between the lips/cheeks, and the gums/teeth. The oral cavity proper is situated behind the vestibule, and is bordered by the roof, the floor of the mouth, and the cheeks.
The roof of the mouth contains of the palate, which is divided into a hard and a soft part. The hard palate is to the front, consists of bone covered by a membrane tissue, and separates the mouth from the nose. The soft palate is smaller, located to the back, has no bone, and reaches an extended projection called the uvula.
Cheeks cover an important part of the face. Their inside parts are covered with an oral mucous membrane that hides the inside of the mouth. Cheeks are made of fat pads and muscles supported by neighbouring bones.
The floor of the mouth is the part of the oral cavity that lies beneath the tongue. It is comprised of muscles (mylohyoid and geniohyoid muscles), of the tongue itself, the lingual frenulum, and ducts of the sublingual and submandibular glands (salivary glands). The floor of the mouth participates in the process of food intake and swallowing.
The mouth also contains the teeth, which are the major component that grind down foods. Gums and their underlying alveolar bone, support teeth and keeps them in place.
The mouth’s main roles are eating, drinking, and speaking. Breathing through the mouth is also an important backup system if there is an obstruction of breathing through the nose.
Digestion is the main role of the mouth. The first component of the digestive tract is the mouth. Digestion starts when food is taken into the mouth, chewed by the teeth, and moistened with saliva. There are enzymes in the saliva (mainly amylase) that help breaking down starches into smaller sugar molecules. The tongue helps to move food around towards teeth so it can be chewed. The tongue then pushes the wet and soft bolus towards the back so it can be swallowed. The epiglottis is a flap of cartilage that closes over the windpipe (trachea) of the respiratory system, to make sure that food is directed towards the oesophagus and then to the stomach. A male’s mouth can hold approximately 71.2 ml of food, while a female mouth may hold 55.4 ml.
Communication by people relies mostly on the use of the mouth. To pronounce words, a series of complex events are involved, and they must happen in the right order. Vocal cords vibrate through air in the larynx, which produces a sound. The type of sound depends on the tightness of the vocal cords and the force of the expelled air. The tongue and the lips move in a precise way to define the sounds. The nose, the hard and soft palates also participate in shaping each sound.
Breathing is primordial for the survival of a person, and it cannot be interrupted. The nose being the main breathing organ, it can sometimes be obstructed (physically or through mucous obstruction). Mouth breathing serves as a backup system when air cannot pass through the nose. But breathing through the mouth only (with no or little breathing through the nose) can lead to problems, such as malocclusion (crooked teeth), facial deformities, and gum disease.
For some disabled people, who through accident or congenital deformity, have lost dexterity in their hands. They use their mouths instead when writing, typing, drawing, painting, or using tools.
Diseases of the mouth
The mouth is a complex environment that contains many parts. Each of these components may be infected or function deficiently.
Therefore, many diseases can affect the mouth, and here are just a few common ones:
Dental cavities are infections of teeth by bacteria. Also called tooth decay, cavities destroy tooth structures and can lead, if not treated, to more serious infections, or to the loss of teeth.
Periodontal disease is the infection and inflammation of gums. It starts with gingivitis, which is infection of the covering gums. If not treated with improved oral hygiene, gingivitis can reach the underlying alveolar bone, by slowing destroying it. This can also lead to serious infections and tooth loss.
Canker sores are ulcers that may be found on any part of the mouth and are painful when drinking or eating. Most are harmless and disappear after 7 to 14 days.
Cold sores are very similar to canker sores, except they are caused by the herpes simplex virus family.
Oral candidiasis, or thrush, is a fungal infection, mainly by Candida ablicans. It looks like a white creamy lesion, and can affect many parts of the mouth.
Oral cancers can form in tissues of the oral cavity or the oropharynx (part of the throat behind the mouth). The main causes of oral cancers are tobacco use and alcohol use.
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