Food contains nutrients. These are substance which the body needs to give it energy and materials for growth. The body can only extract the nutrients from the food when the food has been broken down into small particles.

The first part of the mouth to touch the food are the lips. They are very sensitive to touch and feel the surface of the food. If the food is too hot or too cold nerves in the lips send messages to the brain to stop you taking the food into the mouth.

The second part of the mouth to touch the food are the front teeth. These are called incisors and are shaped like chisels. As the jaws close on the food the incisors cut their way into the food from above and below. Next to the incisor teeth are the canines. They are pointed like daggers and may be used at the same time as the incisors. The points of the canines stab their way into the food and help tear it up.

As the front teeth break off a piece of the food the mouth waters. The water is called saliva and is produced by salivary glands that are under the tongue. The saliva makes the tongue moist so it can taste the food efficiently. Food cannot be tasted if the tongue is dry. Nerves in the tongue carry messages to the brain about the taste of the food. If the food has gone bad it may taste so sour that the brain instructs you to spit it out. If the food passes the taste test the tongue will move it to the back of the mouth to the molar teeth. These teeth have large lumpy surfaces which mash up the food when the jaws close.

When the molar teeth have finished their task the tongue rolls the food into a ball. The saliva helps the mashed up pieces stick together and gives the whole ball a slippery surface so it is easy to swallow.

The mouth takes a great deal of wear as it breaks down the food in over twenty meals a week. The insides of the cheek are continually being worn away. Groups of cheek cells are scrapped off the inside surface of the cheek and swallowed with the food. Below the surface more cells quickly divide to replace those that have been lost. The part of the tooth above the gum is called the crown. It is coated with the hardest substance in the body. This substance is called enamel. The part of the tooth inside the gum. This is long and sturdy and holds the tooth firmly as it cuts, tears, or grinds the food.

Even though the mouth can cope with wear the teeth can be attacked by acids and bacteria and the gums may become inflamed. Problems with the teeth and gums can be controlled by brushing the teeth regularly with toothpaste and avoiding sugary foods which encourage bacteria to live and breed on the teeth.