Human Body Chapter Notes | Science Class 3 ICSE PDF Download

• The human body consists of various parts that work together to perform different activities.
• Each part, called an organ, has a specific role.
• External organs, like eyes, ears, nose, skin, and tongue, are visible.
• Internal organs, such as the brain, heart, lungs, and stomach, are inside the body and not visible.
• A group of organs working together for a specific function forms an organ system.
• The human body has several organ systems, including respiratory, skeletal, muscular, circulatory, digestive, excretory, nervous, reproductive, and lymphatic systems.

Internal Organs of the Human Body

• Internal organs are essential for survival and located at specific places in the body.
• Brain: Found inside the head, protected by the skull; controls all body functions, helps us think, feel emotions, and remember.
• Heart: Located in the chest between the lungs, slightly tilted to the left, protected by the ribcage; pumps blood to all body parts.
• Liver: Positioned on the right side of the abdomen behind the ribs; produces juices to break down food and cleans the blood; it is the largest internal organ.
• Stomach and Intestines: Stomach, a J-shaped organ below the chest, breaks down food into smaller pieces; small and large intestines, below the stomach, further break down food into simpler substances for growth and energy.
• Kidneys: Two kidneys located in the abdomen; filter and remove waste from the blood, which is expelled as urine.

Respiratory System in Humans

• The respiratory system is responsible for breathing, helping us take in oxygen and remove carbon dioxide.
• It includes the nose, windpipe, and lungs.

Organs of the Respiratory System

• Nose: Used for breathing in (inhalation) and breathing out (exhalation); contains fine hair and mucus to trap dust and germs, protecting the lungs.
• Windpipe: Also called the trachea or throat; a passage that carries air from the nose to the lungs.
• Lungs: Two spongy, bag-like structures in the chest cavity, protected by the ribcage; absorb oxygen from inhaled air and remove carbon dioxide during exhalation.

Process of Breathing

• Breathing involves taking in oxygen and releasing carbon dioxide.
• Air enters through the nose, travels through the windpipe, and reaches the lungs.
• In the lungs, oxygen is absorbed, and carbon dioxide is exhaled.
• The diaphragm, a muscle below the lungs, moves up and down to help lungs expand during inhalation and contract during exhalation.

Deep Breathing

• Deep breathing is a method to take in oxygen-rich air, often practiced during yoga or meditation to relax the body and mind.

Simple Process of deep breathing

• Sit comfortably with a straight back in a quiet place and close your eyes.
• Breathe in slowly through the nose, making the stomach expand slightly.
• Hold the breath for a few seconds, then exhale slowly through the mouth, letting the stomach go in.
• Repeat several times to feel relaxed.
• Benefits: Improves oxygen supply to the lungs, enhances overall health, and can be done for a few minutes daily.

Air Pollution

• Air pollution occurs when harmful substances, called pollutants, are added to the air, making it unsafe for living things.
• Pollutants include smoke and harmful gases from human activities.

Causes of Air Pollution

• Smoke from vehicles, factories, forest fires, and bursting crackers.
• Burning wood, coal, leaves, polythene, and garbage.
• Harmful gases from power plants, refrigerators, and air conditioners.

Effects of Air Pollution

• Causes lung diseases like asthma, chest pain, and lung cancer, as well as heart diseases.
• Leads to coughing, dizziness, headaches, skin problems, and irritation in eyes, nose, and throat.
• Harms crops, buildings, and monuments.
• Causes changes in climate and creates holes in the ozone layer, which protects Earth from harmful sun rays.

Ways to Reduce Air Pollution

• Plant more trees to increase oxygen levels.
• Use CNG fuel for vehicles and get regular pollution checks.
• Use public transport instead of personal vehicles.
• Switch off lights and fans when not in use.
• Avoid burning wood, leaves, coal, polythene, or garbage.
• Use jute or cloth bags instead of plastic or polythene bags.
• Recycle paper, plastic, and other waste materials.
• Educate others about reducing air pollution.