The mouth consists of the vestibule and the oral cavity (Figure 9.13). The vestibule is the space between the lips and cheeks on the outside and the teeth and gingivae (gums) on the inside. The palate forms the roof of the oral cavity with the base of the tongue forming the floor of the mouth. It is bordered by the alveolar arches, teeth and gums at either side (Long et al. [112]). The lips and cheeks are formed of skeletal muscle; the inner part of the cheeks is known as the buccal mucosa and consists of columnar epithelium. The lips are involved in speech and facial expression and keep food within the oral cavity. The cheeks control the location of food as the teeth break it down.

Teeth are formed of the crown (the visible part) and the root. The crown is covered in enamel – a hard, dense material that cannot repair itself once damaged. Below the enamel cap, the tooth is formed of a bone‐like material called dentine. This extends into the root and surrounds the pulp cavity, which contains nerve fibres, blood vessels and connective tissue. Where the pulp cavity extends into the root, it is known as the root canal. Teeth are embedded in alveoli (sockets) in the maxilla and mandible and are held in place by periodontal ligaments and a substance known as cementum. Teeth are important in breaking down and grinding food and are also involved in producing sounds in speech (Marieb and Keller [117]).

The tongue is a muscular structure that extends from its tip (apex) to the posterior attachment in the oropharynx. It houses taste buds and is involved in taste, forming food into a bolus and pushing it to the back of the mouth for swallowing. It is also involved in the articulation of sounds in speech.

The palate consists of the hard palate anteriorly and the soft palate, which is a muscular structure leading to the palatoglossal arches and the uvula. The hard and soft palates are involved in mastication, swallowing and production of speech (Hand and Frank [80]).

Saliva is produced by the parotid glands (in front of the ears), which are rich in amylase; the submandibular glands (in the lower part of the floor of the mouth), which produce mucinous saliva; and the sublingual glands (in the floor of the mouth between the sides of the tongue and the teeth), which produce viscous saliva. There are also minor salivary glands in the buccal mucosa (Hand and Frank [80]). On average, 1000–1500 mL can be produced daily, consisting mainly of water with electrolytes, amylase, proteins (such as mucin, lysozyme and immunoglobulin A), and metabolic wastes (Tortora and Derrickson [228]). It is important for mastication, taste and speech. Saliva is also slightly acidic and can act as a buffer; it acts as a defence against infection by physically washing debris off teeth, and saliva proteins have an antibacterial action (Hand and Frank [80]).