The digestive process starts with changing the composite of food, which begins with the teeth and the chemical effects of saliva. This process turns food into what is called a bolus. Deglutition is the process of swallowing food. The mouth performs numerous responsibilities, including receiving food, altering its basic form and structure through the process of chewing, initiating digestion via mastication, and creating the necessary forms for the flow of speech. The mouth is also the secondary air canal for the respiratory system.
The pharynx is positioned just posterior to the mouth. It is designed to be the single pathway for both air and food, and thus is associated with both the respiratory system and the digestive system. Saliva chronically keeps the lining of the pharynx and the mouth moist. The lining of both these structures is created by nonkeratinized stratified squamous epithelium.
The mouth and the oral cavity are basically one in the same. The structures which create the entire cavity include the cheeks, the hard and soft palates, and the lips. There is an obvious exterior depression between the cheeks and the lips, which serves as the vestibule for the oral cavity. Internally, the vestibule is located in the depression between the gums and the cheeks. The oral orifice refers to the opening of the oral cavity, commonly called the mouth. The opening between the pharynx and the oral cavity is known as the fauces.