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Tamil Nadu (TNBSE)Class 3 Science★ 6-8 marks in TN Class 3 Term 1 exams — labelling diagrams, naming organs and functions, short written answers

My Body

Samacheer Kalvi (TN State Board) Class 3 Science — Chapter 1, My Body. Sensory organs and personal hygiene. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

⏱ 10 min readeasy-to-medium difficulty✓ Free · NCERT-aligned

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By the end of this chapter you'll be able to…

1Name the 5 major organ systems: digestive, respiratory, circulatory, skeletal, nervous
2Describe the path of food: mouth → food pipe → stomach → small intestine → large intestine → waste out
3Describe the path of air: nose → windpipe → lungs
4State the function of the heart: pumps blood to all body parts through blood vessels
5Name at least 5 major bones: skull, backbone, ribs, arm bone (humerus), thigh bone (femur)
6State the function of brain and nerves: brain controls everything; nerves carry messages
7List 3 ways to care for the body: balanced diet, daily exercise, good posture

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Why this chapter matters

My Body in Class 3 is a major step up — children go from naming body parts to understanding organ systems. They learn that the body is an interconnected system where the digestive system breaks down food, the respiratory system brings in oxygen, the circulatory system delivers both to every cell, the skeletal system provides structure, and the nervous system controls everything. Understanding how their body works empowers children to take better care of it.

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My Body — Class 3 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 3 Science, Chapter 1. Sensory organs and personal hygiene.

1. About this chapter

This chapter covers My Body as part of the Class 3 Samacheer Kalvi Science curriculum. It deals with sensory organs and personal hygiene and builds conceptual understanding essential for the TN School Term Exam.

By the end of this chapter, students will be able to:

Name the five sensory organs
Practice personal hygiene habits

2. Key concepts

Concept 1: Name the five sensory organs.
Concept 2: Practice personal hygiene habits.

3. Important terms and formulas

Term / Formula	Description
Name the five sensory…	Name the five sensory organs
Practice personal hygiene habits…	Practice personal hygiene habits

4. Worked examples

Example 1. Applying a key concept from this chapter.

Solution: Identify the relevant principle → apply the formula or rule → state the answer with correct units.

Example 2. A typical exam-style question on my body.

Solution: Break the problem into steps, use the appropriate formula and verify the answer.

5. Common mistakes

Mistake: Skipping units or forgetting to state them. Fix: Always write units alongside every quantity and answer.
Mistake: Confusing similar terms or concepts in this chapter. Fix: Make a comparison table of the terms during revision.

6. Practice (exam-style)

Define the main term or principle covered in Chapter 1.
Give two real-life examples related to my body.
Solve a short numerical or descriptive question from this chapter.
State one important formula and explain each symbol.

7. Answer key (hints)

Refer to section 2 (Key concepts) above for the definition.
Examples should be drawn from daily experience and local context.
Apply the formula from section 3, show all steps clearly.
Formula with units — refer to the textbook glossary for symbol meanings.

8. Quick revision

Class 3 Science — Chapter 1: My Body.
Core idea: Sensory organs and personal hygiene.
Key outcomes: Name the five sensory organs; Practice personal hygiene habits.
Always revise diagrams / tables from the Samacheer Kalvi textbook before the exam.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Digestive system

Mouth (chewing + saliva) → Food pipe (oesophagus) → Stomach (churns with acid) → Small Intestine (absorbs nutrients, ~6-7m long!) → Large Intestine (absorbs water) → Waste out.

Most digestion happens in the small intestine, not the stomach. The stomach mainly churns and breaks food down with acid.

Respiratory system

Nose (filters air) → Windpipe (trachea) → Lungs (absorb O₂, remove CO₂). We breathe in oxygen, breathe out carbon dioxide.

An adult breathes about 20,000 times a day. Place your hand on your chest and feel your lungs at work.

Circulatory system

Heart (fist-sized pump, 60-100 beats/min) → Blood vessels (arteries carry blood away, veins bring it back) → Blood carries oxygen + digested food to all cells.

All blood vessels in your body laid end-to-end would stretch ~100,000 km — around Earth 2.5 times.

Skeletal system

Skull protects brain. Backbone (33 vertebrae) keeps us upright. 12 pairs of ribs protect heart and lungs. Femur is the longest bone. Joints (elbow, knee) let bones move. Muscles attached to bones create movement.

Babies have ~300 bones; adults have 206. Many fuse together during growth.

Nervous system

Brain → control centre in the skull. Nerves → thread-like message carriers. Spinal cord → main cable through the backbone. Reflex: touch hot → nerve signals brain in <0.01s → brain signals 'PULL AWAY!' instantly.

The brain controls EVERYTHING — thinking, movement, breathing, heartbeat, emotions, and senses. It works even when you sleep.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Thinking digestion happens only in the stomach

✓ Digestion starts in the mouth, continues in the stomach, but MOST happens in the small intestine.

WATCH OUT

✗ Confusing food pipe (oesophagus) and windpipe (trachea)

✓ Food pipe carries food to stomach. Windpipe carries air to lungs. A flap (epiglottis) covers the windpipe when you swallow to prevent choking.

WATCH OUT

✗ Thinking the brain is only for thinking and studying

✓ The brain controls breathing, heartbeat, digestion, emotions, movement, memory — everything. It never stops working.

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