The New Childrens Encyclopedia

Food f low

We eat to refuel our bodies. We need fuel

from food to provide energy, as well as for

growth and repair. Digestion is the process

by which the food we eat is broken down

to extract the nutrients we need. Waste

matter is then passed out of the body.

TAKE A MOUTHFUL

Digestion begins with ingestion when you

take in and chew food, mixing it with saliva

to make it easier to swallow. Swallowing

moves the food into the esophagus, from

where it goes into the stomach.

u A GOOD CHURNING

A meal spends up to four

hours in your stomach before

being passed slowly on into

the small intestine.

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Beneath the tough

surface enamel,

each tooth has its

own blood supply.

u CHEWING FOOD The bolus

of food is about to be swallowed.

The epiglottis is in its usual position.

u SWALLOWING FOOD On

swallowing, the epiglottis moves

down to close entry to the trachea.

Three muscle

layers enable the

stomach to twist

into different

shapes.

Acid and food

are churned

together.

THE HUMAN BODY

What’s in a tooth?

Humans have four types of

teeth: chisel-shaped incisors

cut, while pointed canines

tear. The flatter premolars

and molars crush and grind.

These are the largest teeth.

Churned food is

passed into the small

intestine.

Whan food arrives

your stomach

stretches to

store it.

Down it goes

Once food has been chewed, it is

swallowed as a ball called a bolus.

It is prevented from entering the

larynx and trachea by the epiglottis,

a flap of cartilage.

■ Inside the stomach Food enters

your stomach about eight seconds

after you swallow. It is mixed with

acids (called gastric juice) and

churned into a semiliquid. Up to

6 pints (3 liters) of gastric juices are

made in the stomach every day.

THE STOMACH AND HOW IT WORKS

Salivary glands

Saliva is produced by

glands in the mouth.

It makes food

slippery and begins

the process of

digestion. About

3 pints (1.5 liters) of

saliva is secreted into

the mouth each day.

Food bolus

Pharynx

Tongue

Epiglottis

Larynx

Trachea

Esophagus

Soft palate

closes nasal

cavity

Food bolus

Pharynx

Tongue

Epiglottis folds

down to cover

trachea

Trachea

Esophagus

Longitudinal Circular Oblique

THE HUMAN BODY

Premolar Canine

Incisor

Molar