LESSON NOTE: THE DIGESTIVE SYSTEM
Subject: Basic Science
Class: Basic 4
Topic: The Digestive System
Duration: 40 minutes
Learning Objectives
At the end of the lesson, pupils should be able to:
1. Explain what the digestive system is.
2. Name some organs of the digestive system.
3. Explain how food moves through the body.
4. State the importance of digestion.
5. Mention ways of keeping the digestive system healthy.
Introduction
Every day, we eat different kinds of food such as rice, beans, yam, fruits, vegetables and meat.
Our body needs these foods for energy, growth and good health. However, the food we eat cannot be used by the body immediately. It must first be broken down into smaller substances that the body can absorb and use.
The process of breaking down food into simpler substances that the body can use is called digestion.
What is the Digestive System?
The digestive system is a group of organs in the body that work together to digest food and absorb nutrients.
The digestive system helps our body to:
– Break down food.
– Absorb useful nutrients from food.
– Get energy from food.
– Remove waste materials from the body.
Main Parts of the Digestive System
The major parts include:
1. Mouth
2. Oesophagus (food pipe)
3. Stomach
4. Small intestine
5. Large intestine
6. Rectum
7. Anus
Other important organs that help digestion include the liver, pancreas and gallbladder.
1. Mouth
Digestion begins in the mouth.
When we eat, our teeth chew the food into smaller pieces. Saliva also mixes with the food and begins the process of digestion.
The tongue helps to mix the food and move it towards the throat.
2. Oesophagus
The oesophagus, also called the food pipe, is a tube that carries swallowed food from the mouth to the stomach.
3. Stomach
The stomach is a bag-like organ.
Food stays in the stomach for some time. The stomach mixes the food with digestive juices and breaks it down further.
4. Small Intestine
The small intestine is a long, narrow tube.
Most of the digested food is absorbed into the blood through the walls of the small intestine.
The nutrients are then carried to different parts of the body.
5. Large Intestine
The large intestine absorbs water from the remaining food material.
It helps to form waste, also called faeces.
6. Rectum
The rectum stores faeces temporarily before they leave the body.
7. Anus
The anus is the opening through which faeces leave the body.
How Food Travels Through the Body
Food generally passes through the digestive system in this order:
Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus
Importance of Digestion
Digestion is important because it:
– Helps the body get nutrients from food.
– Provides the body with energy.
– Helps children grow.
– Helps repair damaged body tissues.
– Helps the body remain healthy.
How to Keep the Digestive System Healthy
We can keep our digestive system healthy by:
1. Eating a balanced diet.
2. Eating fruits and vegetables.
3. Drinking enough clean water.
4. Chewing food properly.
5. Washing our hands before eating.
6. Keeping food clean and covered.
7. Exercising regularly.
8. Avoiding too much junk food.
9. Keeping our environment clean.
Class Activity
A. Fill in the blanks
1. Digestion begins in the __________.
2. The __________ carries food from the mouth to the stomach.
3. Food is mixed with digestive juices in the __________.
4. Most nutrients are absorbed in the __________.
5. The __________ absorbs water from the remaining food material.
B. Answer these questions
1. What is digestion?
2. What is the digestive system?
3. Mention four parts of the digestive system.
4. What is the function of the stomach?
5. Why is the small intestine important?
6. Mention three ways of keeping the digestive system healthy.
Summary
The digestive system helps our body to digest food and absorb nutrients.
Digestion begins in the mouth. Food then passes through the oesophagus, stomach, small intestine, large intestine, rectum and anus.
The nutrients obtained from food help our body to grow, get energy and stay healthy.
Evaluation Questions
1. What is digestion?
2. Where does digestion begin?
3. What carries food from the mouth to the stomach?
4. Name the organ where most nutrients are absorbed.
5. What is the function of the large intestine?
6. What is the function of the anus?
7. Mention three healthy habits that help the digestive system.
Homework
Draw a simple diagram of the human digestive system and label these parts:
Mouth, Oesophagus, Stomach, Small Intestine, Large Intestine, Rectum and Anus.