Digestion begins in the mouth with the mechanical action of teeth and the chemical action of digestive enzymes present in saliva. Salivary amylase breaks starch into the disaccharide maltose. Saliva lubricates the contents of the mouth. The tongue manipulates food into a bolus as it is chewed and initiates the swallowing process. The tongue also secretes lingual lipase, an enzyme that is activated by the acid in the stomach. It chemically digests fat after the food has been swallowed.