Mouth, salivary glands and their functions Mouth is only an opening of the digestive system. Taking in of food digestive system. Taking in of food through mouth is called ingestion. The cavity or space in the mouth is called oral cavity or buccal cavity.
Digestion starts in buccal cavity. Teeth, tongue and openings of three pairs of salivary gland are present in baccual cavity.
Physical and chemical nature of the food changes when it is masticated with the help of teeth and mixed with saliva.