AP 5th Class EVS Concept Notes - 4. Our Body Our Organ system

Our Body – Our Organ System

The human body is composed of many parts working together seamlessly, much like an amazing machine. These body parts are broadly divided into two categories:

👁️ External Organs

Organs located on the outside of the body that are visible to us.

Examples: Head, Hands, Legs, Eyes, Ears, Nose, Teeth, Skin.

🫀 Internal Organs

Organs located inside the body that are protected and not visible from the outside.

Examples: Brain, Heart, Lungs, Liver, Kidneys, Stomach.

What is an Organ System? A group of organs working together to perform a specific major life function for the body.

Major Organ Systems of the Human Body

1. The Skeletal System

The skeletal system forms the structural framework of the body, giving it shape, support, and protection for delicate internal organs.

💀 Skull

Hard bony structure of the head that protects the sensitive Brain.

🫁 Ribcage

Cage-like arrangement of bones that protects the Heart and Lungs.

🦴 Backbone (Spine)

Supports upright posture and protects the delicate Spinal Cord.

• Total Bones: An adult human body has 206 bones.
• Longest Bone: Femur (Thigh bone).
• Shortest Bone: Stapes (Located in the middle ear).
• Muscles & Movement: Muscles are attached to bones. Together, they provide shape, support, and enable movements like walking and bending.
• Cartilage: Soft, flexible tissue found in external parts like the ear and the tip of the nose.

💡 Healthy Bones Tip: Eat calcium-rich food like milk, curd, and eggs. Daily exercise and exposure to early morning sunlight help keep bones strong! Bones can be imaged clearly using X-rays.

2. The Digestive System

Digestion is the process of converting complex food materials into simple, absorbable substances with the help of enzymes and digestive juices.

👄 Mouth
(Chewing & Saliva)

➔

🥖 Oesophagus
(Food Pipe)

➔

🥣 Stomach
(Digestive Juices)

➔

🌀 Small Intestine
(Nutrient Absorption)

➔

🌊 Large Intestine
(Water Absorption)

➔

🚽 Rectum & Anus
(Waste Removal)

Step-by-Step Digestion Pathway:

1. Mouth: Teeth chew and grind food; saliva softens it.
2. Oesophagus: Pushes softened food down into the stomach.
3. Stomach: Food mixes with digestive juices and becomes liquid-like.
4. Small Intestine: A coiled structure approximately 6 meters long. Digestion finishes here, and nutrients are absorbed into the blood.
5. Large Intestine: Absorbs excess water from remaining undigested food.
6. Rectum & Anus: Waste is stored in the rectum and passed out through the anus.

3. The Respiratory System

The respiratory system supplies the body with oxygen to break down food and release energy, and expels carbon dioxide waste.

👃 Nose

➔

🫁 Windpipe (Trachea)

➔

🎈 Lungs

📥 Inhalation

Breathing in air rich in oxygen. The lungs enlarge and expand.

📤 Exhalation

Breathing out carbon dioxide and water vapour. The lungs contract.

4. The Circulatory System

The circulatory system consists of the Heart, Blood, and Blood Vessels. It pumps and transports oxygen, nutrients, and waste throughout the entire body.

❤️ The Heart

Located on the left side of the chest. It acts like a motor pump and makes a "lub-dub" sound. It has 4 chambers:

• Upper 2 chambers: Atria
• Lower 2 chambers: Ventricles

Doctors listen to heartbeat using a Stethoscope.

🩸 Blood Vessels

Arteries: Carry oxygenated (pure) blood away from the heart to body parts.

Veins: Carry deoxygenated (impure) blood back from body parts to the heart.

🩸 Blood & Anemia Info: Blood contains Haemoglobin, an iron-rich protein in red blood cells. A deficiency of RBCs causes Anemia. To prevent this, consume groundnuts, jaggery (chikkies), eggs, milk, and leafy green vegetables.

5. The Excretory System

The excretory system is the body's purification plant that removes waste fluids and toxic materials.

Excretory Organ	Structure	Waste Produced / Eliminated
Kidneys	Two bean-shaped organs in the abdomen	Filters blood to produce Urine
Skin	Largest visible organ with sweat pores	Eliminates excess water & salt as Sweat
Lungs	Spongy breathing organs	Expels Carbon Dioxide & Water Vapour

Urinary System Pathway: Kidneys ➔ Urine Tube (Ureter) ➔ Urinary Bladder ➔ Urethra.

6. The Nervous System

The nervous system acts as the body's control network, transmitting messages between the brain and all parts of the body.

🧠 Brain
(Control Unit)

➔

🦮 Spinal Cord
(Main Trunk)

➔

⚡ Nerves
(Signal Transmission)

Sensory Organs: Eyes, Ears, Nose, Tongue, and Skin connect to the brain via nerves, helping us see, hear, smell, taste, and feel touch.

Summary Comparison of All Organ Systems

Organ System	Key Organs Included	Primary Function
Skeletal System	Bones (206), Skull, Ribcage, Backbone	Provides structure, support, protection, and allows movement.
Digestive System	Mouth, Oesophagus, Stomach, Intestines, Anus	Breaks down food into absorbable nutrients for energy.
Respiratory System	Nose, Windpipe, Lungs	Takes in oxygen for energy and releases carbon dioxide.
Circulatory System	Heart, Blood, Blood Vessels	Transports oxygen, nutrients, and waste across the body.
Excretory System	Kidneys, Skin, Lungs	Removes excess waste fluids and toxins from the body.
Nervous System	Brain, Spinal Cord, Nerves, Sense Organs	Controls and coordinates all body actions and responses.

Key Takeaways & Awareness

• 📅 World Health Day: Celebrated every year on April 7th.
• 🤝 Teamwork of Systems: Organ systems work together. For example, when running, the skeletal and muscular systems move your legs, the respiratory system breathes faster for oxygen, the circulatory system pumps blood rapidly, the skin produces sweat to cool down, and the nervous system coordinates everything!

🌟 Body Awareness Slogan 🌟

"Eat Well, Exercise Daily, Stay Fresh — Take Care of Your Body, It's Your Only Home!"