Teeth are hard, bonelike structures in the upper and lower jaws of human beings and many kinds of animals. They are the hardest parts of the body.
People use their teeth chiefly to chew food. Chewing is the first step in the process of digestion. Digestion begins as the teeth chop and grind chunks of food into smaller pieces. As the teeth chew the food, it is mixed with saliva, a liquid produced in the mouth. The food becomes a moist pulp, which is easy to swallow. The food is further broken down in the stomach and the small intestine, where it is absorbed by the blood. The blood carries the digested food to all parts of the body. Without teeth, people could not eat foods that must be chewed. They could only swallow soft foods and liquids.
Teeth also play an important part in speech. The teeth and tongue are used together to form many sounds that make up words. To produce the th sound, for example, the tip of the tongue is placed against the upper front teeth. A person who lacks these teeth may be unable to make the sound. Teeth also help support the muscles around the mouth and so contribute to a person's appearance. People who have lost their teeth lack this support. Unless they wear artificial teeth, they may have deep, saggy lines around the mouth.
Like human beings, most animals use their teeth to chew food. They also use their teeth to obtain food. Many animals that eat plants tear off the leaves or stalks of the plants with their teeth. Most meat-eating animals use their teeth to seize and kill prey.
