The teeth are involved in cutting and grinding food to increase the surface area. Saliva is added to the food in the mouth. Saliva contains the enzyme salivary amylase, which initiates the chemical breakdown of starch. Saliva also lubricates the oral cavity and helps bind food before swallowing. In addition to having taste buds, the tongue helps position the food between the teeth and push it to the back of the throat for swallowing.
Food then passes down the esophagus to the stomach.
Because both food and air pass through the pharynx , it is important to prevent food from getting into the lungs. During swallowing the larynx is pulled upward . This causes a flap of tissue called the epiglottis to cover the opening to the trachea and prevent food from entering the trachea. In the stomach , additional liquid, called gastric juice is added to the food. Gastric juice contains enzymes and hydrochloric acid.