Final answer:
Saliva, specifically the enzyme salivary amylase, is present in the mouth and performs chemical digestion.
Step-by-step explanation:
Saliva is a watery substance produced in the mouths of many animals and contains various components necessary for chemical digestion. The most important ingredient in saliva for digestion is the enzyme salivary amylase, which breaks down carbohydrates. Saliva also contains mucus for lubrication, immunoglobulins to prevent microbes, and growth factors for wound healing. It acts as a buffer, maintaining a pH conducive to digestion. Saliva starts the process of chemical digestion in the mouth.