The mouth and teeth are the first step in breaking food down. During the process of chewing, food is shredded and ground. Powerful muscles move the mandible, or lower jaw, while the food is chewed. The front teeth cut the food and the back teeth grind the food.

There are three main parts to the tooth: the root, the neck and the crown. The root is the part inside the jaw. The neck is a narrow connection between the root and the crown. The crown of the tooth is above the gum.

First teeth come in between 6 and 8 months. By age 6, baby teeth are gradually replaced by permanent teeth. There are 32 permanent teeth.

When food is being chewed, saliva is squirted into the mouth. Saliva helps to soften the food. It contains an enzyme that helps break down the starch in the food.

After chewing, the food is swallowed and passes down the esophagus to the stomach. The esophagus is about ten inches long. The tongue helps push the food to the back of the mouth, and the muscles in the esophagus move the food down the tube.