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MOUTH

Food enters the body through the mouth. The mouth is the first part of the digestive system, where food is mashed and moistened, so that it can be swallowed. The mouth also plays an essential role in speech and breathing.

WHY IS THE MOUTH ALWAYS WET?

Saliva contains chemicals that kill bacteria, and it flows constantly into the mouth to help keep it free of disease. The mouth’s inner lining also secretes a lubricating fluid called mucus. Saliva and mucus both moisten food, making it easier to swallow.

WHAT HAPPENS TO FOOD IN THE MOUTH?

The front teeth cut up food, and the tongue and cheek muscles push it between the back teeth, where it is ground by the lower jaw. Saliva softens and moistens food and washes over TASTE BUDS in the tongue so that flavors can be identified. The digestive process also begins in the mouth—saliva contains chemicals that break down some foods.

INSIDE THE MOUTH

The mouth is a complex collection of muscles, glands, and other structures that work together smoothly. The tongue alone contains 18 interwoven muscles, which makes it amazingly flexible. Its flexibility is essential for speech, chewing, and swallowing.

TASTE BUDS

Our sense of taste comes from tiny, onion-shaped clusters of cells called taste buds. Most taste buds are scattered across the surface of the tongue, where there are around 10,000, but they are also found in the roof of the mouth and the throat.

WHAT CAN THE TONGUE TASTE?

The tongue is sensitive to four basic tastes: salty, sweet, bitter, and acidic (sour). The chemicals that cause these tastes dissolve in saliva on the tongue and seep into the taste buds, where they trigger receptor cells that send signals to the brain.

FIND OUT MORE

Brain
Digestion
Respiration

Copyright © 2007 Dorling Kindersley

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