Digestive System Class 4 Notes Science

Introduction

Our body gets energy from the food we eat. However, our body cannot use the food in the form it is eaten. It needs to be broken down into simpler forms. The process of breaking down of food into simpler forms is called digestion.

The Digestive System — Parts and Stages

As soon as we bite food, such as a sandwich, it starts a journey through our digestive system. The entire process of digestion takes about 3-4 hours. The different organs of a digestive system are the Mouth, food pipe, stomach, liver, pancreas, small intestine, large intestine and anus. Each of these organs does a different job but together they complete the digestion process.
Digestive system

The process of digestion is given in the flowchart below.

In the mouth

• The teeth in the mouth grind the food into smaller pieces. 
• Saliva present in the mouth makes the food soft and turns it sweet. This happens because saliva converts starch in the food to sugar.

In the food pipe

• From the mouth, the food gets swallowed into the food pipe also known as the esophagus. 
• The food pipe takes the food to the stomach.

In the stomach

• The swallowed food is collected in a bag-like structure called stomach. Here, the food is churned and ground to form a paste and mixed with digestive juices produced by the wall of the stomach.

In the small intestine

• The food that enters from the stomach to the small intestine is partly digested. More digestive juices are added to the food in the small intestine. 
• Bile from the liver and pancreatic juice from the pancreas are added to the food to digest it completely. Thus, the digestion of food ends in the small intestine. 
• Blood absorbs the digested food and delivers it to different parts of the body.

In the large intestine

• The undigested food is now passed on to the large intestine. 
• Here most of the water is absorbed back from the undigested food.

Anus

• The undigested food is thrown out of the body through an opening called the anus.

Edurev Mnemonics:

My Father Started Skiing Last August Mouth Food pipe Stomach Small intestine Large intestine Anus

Teeth

We already know that digestion begins in the mouth and teeth help to break down food into smaller pieces. Now, let us understand about structure and types of teeth. When the baby is about six months old, the teeth start appearing. By the time she is about three years old, she has 20 teeth. These teeth are called milk teeth. At the age of six, the milk teeth start falling out. New teeth appear in their place. These are called permanent teeth. There are 32 permanent teeth in all between the ages of 17 and 21.

Parts of a Tooth

Look in the mirror at your own teeth or see your friend’s smile. The tooth has different parts.

• The part of the tooth we can see is called the crown. The part we cannot see is called the root. It holds the tooth firmly in place. 
• The outer part of each tooth is made of enamel which is a very hard and shiny substance. It protects the inside parts of the tooth. Enamel is the hardest substance in the human body. 
• Dentine lies under the enamel. It is hard but not as much as the enamel. 
• Dentine protects the innermost part of the tooth, called the pulp. It is soft and contains nerve endings and blood supply. The nerve endings inside the pulp send messages to the brain about any sensation. 
• The nerves are connected to the gum through a hole in the root.
• Gums are the pink-coloured soft tissue surrounding the teeth.

Cross-section of tooth

Types of Teeth

Healthy Eating Habits

Apart from eating a balanced diet we also need to do some more things to be fit and healthy. We must follow these in our daily lives.

• Drink at least eight glasses of water every day.
  
• Wash your hands before and after eating.
  
• Always eat freshly cooked food.
  
• Eat a balanced meal. Include plenty of fruits and vegetables as they help in faster digestion of food.
  
• Do not eat too many sweets and chocolates.
• Eat meals at regular intervals. Do not overeat. 

• We should not eat food that is left uncovered because germs present in the air may settle on it and can make us sick.
  
• We should rinse our mouths after every meal. 
• We should not play or exercise immediately after eating our meal.