Digestion
e-learning for Primary Science

Topic Overview

In this topic, you will learn:

• the Function of Digestive System
• the Organs in the Human Digestion System
• the Digestion Process
• and the Path of Digestion

This topic will take about 30 minutes. At the end of the topic, you can take a short assessment.

Function of the Digestive System

We eat food to give our body energy to grow and function properly.

Food has to be broken down into simpler substances that our body can absorb.

The process of breaking down food into simpler substances is known as the Digestion process.

The digestive system does the job of breaking down food into simpler substances.

Digestive juices in the various organs act on food, thereby breaking it into simpler substances.

Organs of the Digestive System

The Digestive system consists of the:

• mouth
• gullet
• stomach
• small intestine
• large intestine
• anus

In the next few sections of this topic  , we will look at the functions of each of these organs and the role they play in the digestion process.

Organs in the Digestion System

The Digestion Process

Digestion begins in the mouth and ends in the small intestine.

Each organ in the digestion system has a role to play.

All the organs have to work together so that digestion and absorption of food can be carried out successfully.

When any one of the organs in the digestive system does not function properly, it will make the absorption of food ineffective and the body will not function properly.

During the digestion process, nutrient absorption takes place in the small intestine while water absorption takes place in the large intestine.

The journey of food in the digestion process takes on a fixed path, from the mouth, to the gullet, then to the stomach, the large intestine, the small intestine and finally waste materials are expelled through the anus.

Path of the Digestion

The path of the travel of food begins in the mouth and ends in the anus. Food first move from the mouth to the gullet, then from the gullet, it is pushed into the stomach. In the stomach, the food is digested where it is further broken down. From the stomach, food travels to the small intestine where more digestion occurs. Nutrient absorption into the blood takes place in the small intestine. The blood will carry the nutrient to all parts of the body. Food not digested in the small intestine is then moved into the large intestine. Water absorption takes place in the large intestine. Waste materials are then expelled through the anus.

Functions of each Organs

Each organ in the digestion system plays a role. They are explained further later.

The mouth

• We chew the food in the mouth to break it into smaller pieces.
• Saliva in the mouth contains certain digestive juices. It mixes with the food with the help of the tongue. Saliva softens the food and makes it easy to swallow.

The Gullet

• The gullet connects the mouth to the stomach.
• The chewed food moves down the gullet and goes into the stomach.
• No digestion takes place in the gullet.

The Stomach

• In the stomach, the food mixes with the digestive juices that are produced in the stomach.
• the food then moves to the small intestine.

The Small Intestine

• more digestive juices are added in the small intestine where the process of digestion is completed.
• The small intestine absorbs the digested food. Blood transports these nutrients to the rest of the body.
• The material that is not absorbed then moves to the large intestine.

The Large Intestine

• In the large intestine, water and some mineral salts are absorbed.
• The waste materials are passed out of the body through the anus as faeces.

The Anus

• Faeces are expelled from the body through the anus.

You have learned

In this topic, you have learned:

• the parts of the digestive system
• the functions of the different parts of the digestive system
• to describe the digestive process
• that different organs work together to carry out the process of digestion

Now, you may do the assessment at the end of the topic.

Assessment