Page 35 - Viva ICSE Science 4 : E-book

3 Human Body—The Digestive

and Excretory Systems

We know that our body is composed of several
organ systems that work together to keep our KEY CONCEPTS

body functioning. In this chapter, we will learn • The digestive system
about the digestive system and the excretory • The excretory system
system. • Healthy food habits related to
digestion and excretion
The food we eat cannot provide us energy
directly. It is fi rst broken down into simpler
forms by our digestive system and absorbed by our body, while the undigested food is

eliminated out by the system. The excretory system, on the other hand, removes excess,
unnecessary or waste materials from our body fl uids like blood and plasma.

Let’s learn more about the digestive and
excretory systems.
mouth
food pipe
The Digestive System

The digestive system is the organ system that
deals with the digestion of food. The process
by which food is broken down into simpler liver stomach

forms so that it can be easily absorbed by
the body is called digestion. It comprises large
small intestine
of a series of organs which include mouth, intestine
food pipe, stomach, liver, small intestine, rectum
anus
large intestine, rectum and anus.

Organs of the digestive system The digestive system

Mouth is the fi rst organ of the digestive system from where we take in food. It consists

of teeth and tongue. Digestion begins in the mouth itself with chewing. The teeth help
to bite and chew food to break it into smaller pieces, which then mixes with saliva. Saliva
is the watery substance produced in the mouth that makes the food soft and helps to
swallow it easily. Tongue, the fl eshy organ in the mouth helps in mixing the food with

saliva and then swallowing it down the food pipe.

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