Maharashtra Board Class 5 EVS Part I Chapter 21 Busy at Work our Internal Organs PDF Download

Busy At Work - Our Internal Organs

Can You Recall?

Take a large sheet of thick paper. The paper should be about the height of a child in the class. Put it on the wall as shown in the picture. Secure it with tapes.

Ask one student to stand against it. Ask another student to draw the outline of the body.

Now get other students to point out the right places of the following organs within the outline. These organs are: the brain, lungs, heart and stomach.

Now recall the following details about each of the organs.

In which cavity of the body is it situated?

What is its function?

Which are the bones that protect it?

Try This

Use a watch to count how many times you breathe in one minute when you are sitting comfortably. From this, work out approximately how many times you breathe in an hour.

Can You Tell?

What bodily needs or sensations do you become aware of even though you are reading a book?

Processes like respiration and digestion go on inside the body continuously. These processes happen with the help of certain organs. Let us learn something about these processes and the organs that carry them out.

Teacher's Note

Our body is working all the time, even when we sleep. Just like a factory has different departments, our body has different organs doing different jobs.

Exam Trick

Remember the four main organs: Brain, Heart, Lungs, and Stomach. Write them down and draw pictures of where they are in the body to remember them easily.

Points to Remember

Our body needs air, water and food to live.
We breathe continuously to get oxygen from the air.
Different organs do different jobs in our body.
These organs are protected by bones.
We must understand how each organ works.

Respiration

We need air, water and food to live. It is necessary for the body to get a continuous supply of oxygen. We get this oxygen from the air, through breathing. That is why we breathe continuously.

In our body, there are organs that carry out the work of respiration. Read their names in the diagram and also their description.

The Respiratory System

The diagram shows our respiratory organs. When we inhale, the air from outside goes into the trachea. It goes through its branches into the lungs. In the lungs, these branches divide further into smaller and smaller branches. At the end of the last branches, there are air sacs or alveoli.

Between the thoracic cavity and the abdominal cavity, there is an organ like a flexible sheet. It is called the diaphragm.

The Diaphragm And Its Movement

When the diaphragm moves downward, we breathe in and the incoming air fills the alveoli in the lungs.

When the diaphragm moves upwards, air in the lungs is pushed out.

Teacher's Note

The diaphragm is like the floor of a lift. When it goes down, air comes in. When it goes up, air goes out. This is how we breathe.

Exam Trick

Remember: Diaphragm down = Breathe in. Diaphragm up = Breathe out. It is like a simple up and down movement.

Points to Remember

The nose filters the air we breathe.
The trachea or windpipe carries air to the lungs.
The lungs contain tiny air sacs called alveoli.
The diaphragm is a muscle that helps us breathe.
Breathing happens automatically without our thinking.

Exchange Of Gases

Dust and smoke particles may be present in the air in the atmosphere. There may even be disease producing micro-organisms. They are harmful for the body.

The inner lining of the respiratory organs has fine hairlike structures called cilia. On this inner lining, there is also a layer of a sticky substance called mucous. The dust and smoke particles stick to this substance. Thus, the harmful substances in the air cannot reach the lungs.

When the outside air reaches the alveoli, the oxygen in it passes into the thin blood vessels around the alveoli. With the blood, it flows to all parts of the body. At the same time, the carbon dioxide that is brought by the blood from all parts of the body enters the air in the alveoli. When we exhale, the carbon dioxide is also given out with the air.

In this way, an exchange of oxygen and carbon dioxide gases takes place in the alveoli.

Do You Know?

Dust and smoke particles may be present in the air in the atmosphere. There may even be disease producing micro-organisms. They are harmful for the body.

The inner lining of the respiratory organs has fine hairlike structures called cilia. On this inner lining, there is also a layer of a sticky substance called mucous. The dust and smoke particles stick to this substance. Thus, the harmful substances in the air cannot reach the lungs.

Try This

Count how many times you breathe in one minute just after you have run a hundred metres.

Get someone else to count how many times you breathe in one minute while you are asleep. What is the difference in the two counts?

Teacher's Note

When we exercise, we need more oxygen, so we breathe faster. When we sleep, we need less oxygen, so we breathe slower. This shows our body is smart.

Exam Trick

Remember: More exercise = Faster breathing. More rest = Slower breathing. Our body automatically speeds up or slows down breathing.

Points to Remember

Cilia are tiny hairlike structures in the respiratory organs.
Mucous is a sticky substance that traps dust and germs.
Oxygen passes from the lungs into the blood.
Carbon dioxide passes from the blood into the lungs.
This gas exchange happens in the alveoli.

Digestion

Let us now learn something about the alimentary canal, the digestive organs and their functions.

The Effects Of Smoking

If one keeps smoking over a long period of time, the toxic substances in the smoke collect in the respiratory tract. As a result, the air that enters the lungs is not sufficiently purified and the impurities in the air begin to accumulate in the lungs. As a result, the efficiency of the lungs is reduced. The likelihood of getting diseases of the lungs increases.

The solid particles in the tobacco smoke from the cigarette or bidi form a sticky layer inside the alveoli. This reduces the amount of oxygen supplied to the body. In addition, some toxic substances in the tobacco also enter the alveoli. These ill effects lead to diseases of respiratory organs including life-threatening diseases like lung cancer.

Passive Smoking

If there are people around us who smoke, then we may have to face the consequences of smoking even if we do not smoke ourselves.

That is why, there is now a ban on smoking in public places.

Teacher's Note

Smoking is very bad for our body. Even if someone else smokes near us, it can harm us. We should always stay away from smoke.

Exam Trick

Remember: Smoking damages lungs. It makes alveoli dirty with tar and poison. This reduces oxygen supply to the body.

Points to Remember

Smoking collects toxic substances in the respiratory tract.
Tobacco forms a sticky layer in the alveoli.
Smoking reduces oxygen supply to the body.
Smoking can cause lung cancer and other diseases.
We should avoid places where people are smoking.

The Alimentary Canal

The food we eat is digested in our body. That is, substances that can mix with the blood are formed from the food. This process takes place in different parts of a long and flexible tube inside our body. This tube is called the alimentary canal. The upper end of this tube is the mouth and the lower end is called the anus.

Even if there is a continuous tube going from the mouth to the anus, the shape of this tube is not the same in all its parts.

A New Word

Gland - An organ that secretes a certain substance.

Teacher's Note

The alimentary canal is like a long food processing factory inside our body. Food enters at one end and waste comes out at the other end.

Exam Trick

Remember: Alimentary = related to food. Canal = a tube. So alimentary canal is the food tube from mouth to anus.

Points to Remember

The alimentary canal is a long tube inside the body.
It starts from the mouth and ends at the anus.
Food is digested in different parts of this tube.
The tube has different shapes in different parts.
Digestion converts food into substances that can mix with blood.

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