Page 42 - Science class 4

DIGESTION

All living beings need energy. Food is the main source of energy. Food may not
be in a form that the body can use directly. It has to be changed into a simple

and usable form. Digestion is the process of breaking down food into simpler
forms so that it can be used by the body. Digested food is absorbed by the

blood and taken to all the parts of the body.
The digestive system helps the body to digest the eaten food.

P P
Process of Digestionrocess of Digestionrocess of Digestion
Mouth (oral cavity)
Pharynx Digestion begins in the mouth itself. When
Tongue
we start eating, our teeth break up the
Esophagus Salivary
Liver glands food into smaller pieces.
The liquid in our mouth called saliva helps
us to digest the food. Saliva softens the

food and changes it into pulp.

The tongue then pushes bits of this
mashed food into the throat where it is

swallowed.
From the mouth the food passes through

the food pipe into the stomach.
Gallbladder
The stomach plays an important role in
Small
intestine digestion. It is a hollow, muscular bag. The
strong muscles of the stomach use
digestive juices to digest the food. It

Rectum changes the mashed food into a semi-solid
Large
intestine form.
Appendix Pancreas Food remains in the stomach from one to
Anus
Stomach
four hours.
Human Digestive This is why we feel full in the evening after

System
a very heavy afternoon meal.

When the stomach has finished its work, muscles at the lower end of the
stomach open. The liquid food now moves to the small intestine.

Digestion is completed in the small intestine . The liver , gallbladder and the
pancreas help the small intestine to complete the digestion process. The liver

secrets bile which helps to digest fats.