3rd Class Science Our Body Our Body

Our Body

Category : 3rd Class


This lesson will help you to:-

  • learn about the different sense organs of our body
  • understand the functions of various internal organs of our body
  • study skeletal system, nervous system, muscular system, respiratory system, digestive system and circulatory system.
  • study the function of heart.


Real Life Examples

                We Got the Beat

  • How does the heart beat? Before each beat, your heart fills with blood. Then its muscle contracts to squirt the blood along. When the heart contracts, it squeezes – try squeezing your hand into a fist. That’s sort of like what your heart does so it can squirt out the blood. Your heart does this all day and all night, all the time. The heart is one hard worker!



Our body is an amazing machine. Each and every part works perfectly in coordination with each other. Our body is made up of different parts called organs. Each and every organ has its own role to play.

1. Sense organs: There are five sense organs namely eyes, ears, nose, tongue and skin which help us to see, hear, smell, taste and feel respectively. They take messages from outside and send them to our brain through nerves. Our brain after receiving these messages order different organs to work accordingly.



2. Skeletal system; Ail the bones of our body together form skeletal system and form the framework of the body. It gives the shape of the body and support the body to stand, sit, and walk.

The adult human skeletal system consists of 206 bones. Human infants are born with 300 to 350 bones, some of which fuse together as the body develops. By the time most children reach the age of 9 they have 206 bones. The skeletal system performs vital functions — support, movement, protection, blood cell production, calcium storage.


3. Nervous system: Nervous system consists of brain and nerves. Made up of your brain, your spinal cord, and an enormous network of nerves that thread throughout your body, the nervous system is the control center for your entire body. Your brain uses information it receives from your nerves to coordinate all of your actions and reactions. It controls all your actions of seeing, hearing, speaking, thinking etc.



4. Muscular system: Muscular system is made up of muscles. On average, probably 40% of your body weight is in muscles. You have over 630 muscles that move you. Without muscles you couldn't open your mouth, speak, shake hands, walk, talk, or move your food through your digestive system. There would be no smiling, blinking, breathing.



5. Respiratory system: The work of your respiratory system is very simple; it brings oxygen into your body, and removes the carbon dioxide from your body. Your body needs oxygen to survive. The main organs in your respiratory system are your lungs. Your lungs are, in their simplest form, nothing more than sacs. As you breathe in, you fill these sacs with fresh oxygen-rich air. Your heart pumps blood into the walls of your lungs where it absorbs oxygen and releases carbon dioxide. As you exhale, or breathe out, you release the carbon dioxide-rich air into the space around you. With each breath you take, you are taking oxygen in, and putting carbon dioxide out. From your lungs, blood returns back into your heart where it is pumped out to the rest of your body, carrying oxygen along with it.



6. Digestive system: The digestive system allows your body to get the nutrients and energy it needs from the foods you eat. The food we eat is in the complex form. The body cannot use it till it is broken down into a simple form. The organs of the digestive system break down food into a simple form. The digestive juices in the stomach help to make it into a soluble form. The food is now digested and easily absorbed by the villy of small intestine into blood.




  • An adult's intestines are at least 25 feet. Be glad you're not a full-grown horse ... their coiled-up intestines are 89 feet long!
  • Chewing food takes 5-30 seconds
  • Swallowing takes about 10 seconds
  • It takes 3 hours for food to move through the intestine
  • In your lifetime, your digestive system may handle about 50 tons of food!!


Digestive Diseases

How To prevent Digestive Diseases

Uneasiness and indigestion causes due to overeating or not chewing food properly. Diarrhea and vomiting occurs when germs or bacteria enter the body through infected food.

We should eat healthy food, i.e. lots of green vegetables and fruits. Food should not be eaten fast;

rather it should be chewed properly. We should also drink plenty of water for proper digestion of food


7. Excretory system: This system helps in removing wastes from your body. The kidneys, lungs and skin helps in removing wastes from your body in the form of urine, carbon dioxide and sweat respectively.


8. The Heart and Circulatory system: The heart and circulatory system make up the network that delivers blood to the body tissues. With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to all of our cells. The circulatory system is compo sed of the heart and blood vessels, including arteries, veins and capillaries. Your heart is really a muscle. It is located a little to the left of the middle of your chest, and it's about the size of your fist. Your heart is like a pump or two pumps in one. The right side of your heart receives blood from the body and pumps it to the lungs. The left side of the heart does the exact opposite: It receives blood from the lungs and pumps it out to the body.


9. Reproductive System: Living organism produces offspring of its own kind to increase its number and to maintain the balance in the nature. Reproductive system performs the process of reproduction. Reproductive system is very essential for new life.


Amazing Facts

  • you have over 30 facial muscles which create looks like surprise, happiness, sadness, and frowning.
  • Eye muscles are the busiest muscles in the body. Scientists estimate they may move more than 100,000 times a day!
  • The largest muscle in the body is the gluteus maximum muscle in the buttocks.


Misconcept/ Concept

Misconcept: While sleeping you can smell.

Concept: You have no sense of smell when you’re sleeping

Misconcept: Babies can see every-thing when they are born

Concept: All babies are colour blind when they are born, So they only see black & White

Misconcept: Bones are very hard and solid

Concept: The outside of a bone are hard; but they are light and soft inside. They are about 75% water.

Other Topics

Notes - Our Body

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