homework encyclopedia

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.

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 flavours can be identified. The

digestive process also begins in the mouth, as saliva

contains chemicals that break down some foods.

WHAT CAN THE TONGUE TASTE?

The tongue is sensitive to five basic tastes: salty,

sweet, bitter, acidic (sour), and umami (savoury).

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.

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.

WHY IS THE MOUTH ALWAYS WET?

Saliva contains chemicals that kill bacteria, and

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.

FIND OUT MORE. Brain 139 • Digestion 144–145 • Respiration 136

4 SURFACE OF THE TONGUE

The surface of the tongue is

covered by tiny bumps called

papillae, which give it a rough

texture to grip food. Most are

small filliform papillae (shown in

blue) that have a sense of touch.

Scattered among these are larger

fungiform papillae (shown in

pink), which contain taste buds.

1 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.

4 TASTE BUDS

This magnified view of papillae

on the tongue shows the taste

buds in their sides. Each taste bud

has a tiny opening, or taste pore,

to let in the dissolved flavours of

food and drink.

Mouth

TONGUE 3

Until recently, it was

thought that a specific area

of the tongue was sensitive

to a particular taste. It is now

understood that a taste, such

as bitter, can be located on

different parts of the tongue.

TASTE BUDS

The surface of

the muscular tongue

is covered by tiny

bumps called papillae

Sublingual

salivary gland

is located under

the tongue

Submandibular

salivary gland

lies deep in

the mouth

Parotid salivary gland

lies in front of the ear

Tongue

moves food

during chewing

and swallowing

Saliva pours into the

gap between papillae

The oesophagus
leads to the
stomach

Taste buds contain

25–30 receptor cells

Salivary duct

opens into

the cheek

Teeth

cut and

grind food

Larynx

Epiglottis

mouth