Food begins its journey from the mouth. The main parts of the mouth are: teeth, tongue and salivary glands. In the mouth, food particles are broken down physically with the help of teeth. It is known as mechanical digestion. Saliva, the watery secretion of the salivary glands, moistens and lubricates the food. Saliva starts the chemical digestion of the food by breaking down the starch present in the food.
As food is chewed, it is mixed with the saliva secreted from the salivary glands. Salivary glands are a group of sac-like alveoli, which form small lobules. These lobules house small ducts which secrete saliva. The principle salivary glands are: parotid, submandibular and sublingual. The saliva moistens the food and starts the chemical digestion of food by secreting starch-digesting enzyme amylase (ptylin). Starch is broken down into soluble form of sugar and maltose.
Lobules :Tiny lobe-type structures