4th Class Science Our Body Our Body

Our Body

Category : 4th Class


This lesson will help you to:

  • understand various internal body parts.
  • know about the function of teeth.
  • learn about food and digestion.
  • study the importance of sanitation and diseases.



Some of the important body systems which include the vital organs are:

1. Circulatory system: All parts of our body need oxygen and nutrients. This work is done by our blood. The blood is circulated throughout the body. The organ which circulates the blood is our Heart. It pumps the blood. The blood flows through blood vessels. Heart and blood vessels together form circulatory system. Blood vessels are of three types: artery, vein and capillary. Our heart is protected from injuries by our ribs. The ribs form a cage like structure to protect the heart from any external damage. There are 12 pairs of ribs in human beings.


2. Respiratory system: We take oxygen inside and give out. The respiratory system regulates the exchange of gases. It is mainly about taking oxygen inside and the waste gases such asout of the body. It includes:

  • Nose: We take air inside through the nose. There are small hairs in the nose which prevent the entry of dust particles.
  • Pharynx: From nasal cavity air goes to pharynx from where it goes to trachea. Tracheas are attached to lungs.
  • Lungs: These are the major respiratory organs where the exchange of gases takes place.


3. Nervous system: It coordinates all the actions of our body. It mainly consists of brain.

Brain: It is the part of our body which controls all the actions of body.

Example: walking, talking, swallowing, taste and smell etc all are regulated by our brain. In short we can say anything we do, our brain is involved in it.

4. Teeth and its functions: We have two sets of teeth during our lifetime; they are milk teeth/deciduous. Teeth and permanent teeth. There are altogether 20 deciduous teeth and 32 permanent teeth.



Transparent or milky white colour.

The hardest tissue in a human body (harder than bone)



Slightly yellowish in colour



Filled with blood vessels and nerve fibres.

We have different types of deciduous teeth: incisors canines, first molars, and second molars. Incisor - to cut food like a pair of scissors. Canine - to tear food like a fork. First molars - can grind food. Second molar – larger than first molars, can grind food like first molars do.



Food needs to be broken down and chewed before entering the digestive system so that our body can easily absorb nutrients from them. This important function is performed by teeth.

5. Food and Digestive system: All the living beings need food to survive and grow. We take our food inside through our mouth and chew it with our teeth. You are already familiar with the types of teeth in our mouth.



Misconcept: Both the lungs are of equal size.

Concept: Your right lung is bigger than left lung! The left lung is small so as to adjust heart in that part.

Misconcept: Brain controls the body equally.

Concept: Left-hand side of your brain controls right side of your body whereas right-hand side controls left part of body

But have you ever thought what happens to our food after we chew it and take it inside? There are many internal organs which help our food to get digested and take energy from it.

The process which allows our body to get the nutrients and energy from food is called digestion.

The digestion starts right from when our food is in our mouth. The saliva in our mouth gets mixed with food and makes it easy to swallow. Our teeth divide the food in small particles and then it is swallowed. The food goes in to esophagus which is a long pipe. Through this pipe food goes into stomach.

When the food enters the stomach it gets mixed with the gastric juices that come from stomach walls. These juices help the food to get digested and kill the bacteria in the food if there is any. After this, the food enters the small intestine which breaks the food further so that our body can absorb all the vitamins, minerals, carbohydrates and proteins from it. After this the food goes into large intestine. Here no digestion of food occurs. The large intestine absorbs the additional quantity of water.


6. Excretory System: The excretory system helps us to get rid of our body wastes. The main organs of this system are:

  • Kidneys: There is a pair of kidneys in human beings which are located below the rib cage. These are the major excretory organs which filter our blood.
  • Ureters: They carry urine from kidneys to urinary bladder.
  • Urinary bladder: It stores the urine temporarily.
  • Urethra: The urine is released to outside through urethra.


7. Immune System: Now we know that many organs together form systems in our body and each system performs different function in our body. But we have to protect our body against diseases and infections also. This role is played by the immune system of our body. It is basically a defense system like an army protects its country against enemies; immune system protects our body against diseases. Just like the army has weapons to fight against enemies, immune system uses antibodies to fight against infections and diseases.


Historical Preview

  • Fingerprints have been found on ancient Babylonian clay tablets, seals, and pottery. Fingerprints were used as signatures in ancient Babylon signatures in the second millennium BCE.



Our body helps us to fight against diseases with its, immune system. But it can protect us upto certain limit 1 only. We have to take proper care of our body to keep it free from diseases. Also by keeping our surroundings and food clean we can avoid diseases.                      

If we do not keep ourselves and our surroundings clean we can fall prey to diseases such as:            

  • Cholera: It is caused by using contaminated water and food.
  • Food Poisoning: is also caused by contaminated food.
  • Typhoid: It is also caused in much the same way as cholera.

So, in order to prevent ourselves from these deadly diseases we should keep some things in mind always.

These are:

  1. Always keep you body clean.
  2. For a clean body we should take bath daily. We should brush our teeth at least twice daily.
  3. We should keep our surroundings clean.
  4. Never let the water to collect at any place as it becomes the place for mosquitoes to breed. These mosquitoes can cause malaria, dengue 01 chickungunya.
  5. Do not let the garbage collect in your surroundings. It attracts the flies which contaminate the food.
  6. Always keep the eatables at a neat place where there are no flies.
  7. Wash the vegetables and pulses thoroughly with clean water before cooking them.
  8. Always wash your hands before cooking food.
  9. Wash your hands properly before and after eating your food.
  10. Cover your food properly.
  11. Always eat in clean plates.
  12. Eat your food at a clean place.

So we can keep our selves healthy if we keep our body and surroundings clean.


Amazing Facts

  • In normal human beings heart beats nearly 72 times in a minute.
  • There is a flap called epiglottis which flops down over the opening of wind pipe to prevent the food from entering in it.
  • The small intestine is 22 feet long.

Other Topics

Notes - Our Body
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