Organ Systems in Our Body - Class 3 Notes & Olympiad Questions

Human Body

1. Our body is made up of different parts, like hands, legs, eyes, ears, and more. Each of these parts has its own special job to do. We call these parts organs.

2. Some of our organs, like the eyes, ears, nose, skin, and tongue, are on the outside of our body. We can see and touch them. We call them our external organs.

3. But there are other organs inside our body that we can't see from the outside. They are located deep inside us. These organs, such as the brain, lungs, heart, and stomach, do important jobs to keep our body working properly. We call them our internal organs.

Internal Organs

Bone and Muscle

a) Our body is made up of 206 bones, which together form our skeleton. The skeleton provides structure and support to our body.

b) We also have over 600 muscles that are attached to our bones. These muscles work together to help us move.

External Organs - Sense Organs

Types of Teeth

There are different types of teeth that work together to help us properly chew and digest different kinds of food. These are:

1. Incisors

a) These teeth are located at the front of our mouth. We have four incisors in each jaw.
b) They have a sharp cutting edge that helps us cut and bite into food. Herbivores, animals that eat plants, often have bigger incisors.

2. Canines

a) Canines are situated on the sides of the incisors. They are sharp and pointed, and their main job is to tear food.
b) In carnivores, animals that eat meat, canines are usually the longest teeth and slightly curved. There are two canines in each jaw.

3. Premolars

a) Premolars are found at the back and sides of the jaw. They help break down the food into smaller pieces before swallowing.
b) They are placed next to the canines and assist in cracking the food. There are four premolars in each jaw.

4. Molars

a) Molars are located at the back and sides of the jaw, after the premolars. They are responsible for grinding food. In each jaw, there are six molars.
b) In herbivores and omnivores, animals that eat both plants and meat, both premolars and molars have a flat surface that aids in chewing.

Main Organ Systems and their Functions

In our body, there are different organs that work together to perform specific functions. When several organs perform the same function, they come together to form an organ system.

There are different organ systems in our body that perform specific functions:

Nervous System

1. The nervous system includes the brain, spinal cord, and nerves. It controls actions and reactions in our body.
2. The brain sends messages to different body parts through nerves and also controls our sense organs.

Excretory System

1. The excretory system helps us get rid of waste materials from our bodies. It consists of two kidneys that filter liquid waste from the blood to produce urine.
2. The skin also removes excess water and salt through sweat.

Circulatory System

1. The circulatory system is made up of the heart, blood, and blood vessels.
2. It transports blood from the heart to various body parts, carrying oxygen and nutrients.
3. It also removes carbon dioxide and other waste materials. Blood is pumped by the heart and circulates throughout the body.

Muscular System

1. The muscular system consists of muscles that cover our entire body. Muscles are attached to bones and help us move.
2. They are present in all the organs in our body.

Skeletal System

1. The skeletal system is formed by all the bones in our body. It provides shape and structure to our body and supports our organs.
2. Joints are present where two bones meet, allowing movement.

Respiratory System

1. The respiratory system includes the nose, windpipe, and lungs. It helps us breathe air.
2. We inhale air through the nose, which then travels down the windpipe into the lungs.
3. The exchange of oxygen and carbon dioxide happens in the lungs.

Digestive System

1. The digestive system breaks down food into simpler forms that can be easily absorbed and used by the body.
2. It includes organs such as the mouth, oesophagus, stomach, liver, pancreas, small and large intestines, rectum, and anus.
3. Digestion starts in the mouth and ends in the rectum, where waste matter is eliminated.

Reproductive System

1. The reproductive system is different for males and females and ensures the survival of the species.
2. It includes organs responsible for reproduction.

Each of these organ systems plays a vital role in maintaining our body's functions and overall health.