Chapter 1 of 10

10%

Tamil Nadu (TNBSE)Class 5 Science★ 7-8 marks in TN Class 5 Term 1 exams — fill in the blanks, choose the correct answer, true or false, match the following, short answers, and diagram-based questions

Organ Systems

Samacheer Kalvi (TN State Board) Class 5 Science — Chapter 1, Organ Systems. Human body systems and their functions. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

⏱ 12 min readMedium difficulty✓ Free · NCERT-aligned

Worksheet

Podcast

Listen as a conversation

A teacher & a student talk through the chapter — in your language.

Mind Map

The chapter at a glance

Every concept and exam-favourite branch — revisable in 5 minutes.

…

Study Guide

Night-before notes

Key points, glossary and the questions most likely to show up.

…

VocabularyBuild your vocabularyLexiGenome mines the key words and schedules them with spaced repetition.Mine words →

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

1State that the human body has 11 major organ systems: digestive, respiratory, circulatory, excretory, nervous, skeletal, muscular, integumentary (skin), endocrine, lymphatic, and reproductive
2Define a cell as the basic unit of life — all living things are made of cells
3Define an organ system as a group of organs that work together to perform a specific function (e.g., mouth, stomach, and intestines work together in the digestive system)
4State key facts: the liver is the largest internal organ; alveoli are the tiny balloon-like air sacs in the lungs where oxygen enters blood and CO₂ leaves; the nephron is the functional filtering unit of the kidney; digestive juices in the stomach break down food into simpler substances
5Describe the respiratory system: we breathe in oxygen through the nose → travels down the windpipe (trachea) → enters lungs → oxygen passes into blood through alveoli → we breathe out carbon dioxide
6Describe the excretory system: kidneys filter blood to remove waste and excess water → produce urine → urine travels through ureters → stored in urinary bladder → expelled through urethra
7State that the nervous system controls all functions of the human body

💡

Why this chapter matters

Organ Systems is the most comprehensive human biology chapter in primary school. For the first time, children learn that the human body has 11 major organ systems — not just a few. They understand that a cell is the basic unit of life, that organs are made of tissues which are made of cells, and that systems are groups of organs working together. They study key facts: the liver is the largest internal organ, alveoli are the tiny air sacs where gas exchange happens in the lungs, nephrons are the filtering units of the kidneys, and the nervous system controls everything. This chapter bridges primary science to the detailed biology of Classes 6-10.

Before you start — revise these

A 5-minute refresher here will save you 30 minutes of confusion below.

🔗

Organ Systems — Class 5 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 5 Science, Chapter 1. Human body systems and their functions.

1. About this chapter

This chapter covers Organ Systems as part of the Class 5 Samacheer Kalvi Science curriculum. It deals with human body systems and their functions and builds conceptual understanding essential for the TN School Term Exam.

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

Name and describe all human organ systems
Explain the role of each organ system

2. Key concepts

Concept 1: Name and describe all human organ systems.
Concept 2: Explain the role of each organ system.

3. Important terms and formulas

Term / Formula	Description
Name and describe all…	Name and describe all human organ systems
Explain the role of…	Explain the role of each organ system

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 organ systems.

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 organ systems.
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 5 Science — Chapter 1: Organ Systems.
Core idea: Human body systems and their functions.
Key outcomes: Name and describe all human organ systems; Explain the role of each organ system.
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.

Cell → Tissue → Organ → Organ System → Organism

Cell (basic unit of life) → Tissues (groups of similar cells) → Organs (groups of tissues working together, e.g., stomach, heart, lungs) → Organ Systems (groups of organs, e.g., digestive system = mouth + stomach + intestines) → Organism (the whole living body).

The human body contains about 37 trillion cells. Each cell is alive — it takes in nutrients, produces energy, and performs its specific function. Red blood cells carry oxygen, nerve cells transmit signals, muscle cells contract.

Key organ facts (from TN Class 5 textbook)

Liver → largest internal organ, produces bile for fat digestion, stores energy as glycogen, detoxifies harmful substances. Alveoli → tiny balloon-like air sacs in lungs (300-500 million in adult lungs), site of gas exchange — O₂ enters blood, CO₂ leaves blood. Nephrons → microscopic filtering units in kidneys (~1 million per kidney), filter waste (urea) and excess water from blood to form urine. Digestive juices → stomach produces hydrochloric acid and enzymes that break down proteins.

The liver is the only internal organ that can REGENERATE — if part of it is removed, it can grow back to full size. This is a unique ability among internal organs.

Respiratory system pathway

Nose/mouth (air enters) → Trachea (windpipe) → Bronchi (two branches, one to each lung) → Bronchioles (smaller branches) → Alveoli (air sacs where O₂ enters blood and CO₂ leaves). We breathe IN oxygen (for cells to produce energy) and breathe OUT carbon dioxide (a waste product).

Breathing is partly voluntary (you can hold your breath) and partly involuntary (you breathe automatically while sleeping). The brainstem (medulla oblongata) controls automatic breathing.

Excretory system pathway

Blood enters kidneys through renal arteries → Kidneys filter blood through millions of nephrons → Waste (urea, excess water, salts) becomes urine → Urine flows through ureters (tubes) → Stored in urinary bladder → Expelled through urethra. The kidneys filter about 180 litres of blood daily, producing about 1-1.5 litres of urine.

If the kidneys fail, waste builds up in the blood and the person needs dialysis — a machine that filters blood externally — to survive.

⚠️

Common mistakes & fixes

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

WATCH OUT

✗ Confusing the largest organ (skin) with the largest INTERNAL organ (liver)

✓ Skin is the largest ORGAN overall — it covers about 2 square metres. But skin is external. The liver is the largest INTERNAL organ — it weighs about 1.5 kg in an adult.

WATCH OUT

✗ Thinking the stomach is where all digestion happens

✓ The stomach breaks down food with acid and enzymes, but MOST digestion and absorption happens in the small intestine. The stomach mainly digests proteins and churns food into a semi-liquid paste called chyme.

WATCH OUT

✗ Thinking the lungs are hollow balloons

✓ Lungs are spongy organs filled with millions of tiny air sacs (alveoli). They are not hollow — they are more like a dense sponge. When you inhale, the alveoli fill with air; when you exhale, they empty.

AI helpers for this chapter

Generate more practice on the fly, or have the chapter explained at a different level.

⚡

Generate 5 more questions

Fresh MCQs + short-answer items based on this chapter, plus answer keys.

🧠

Explain at a different level

Re-explain the chapter at the level you actually want.

📝 My notes

Saved on this device — sign in to sync · how this works

0/600

Practice more, ask doubts, find a tutor

Tamil Nadu (TNBSE) Class 5 mock tests

Tamil Nadu (TNBSE) Class 5 PYQs

Ask in Q&A

Science flashcards

Related chapters

Students who read Organ Systems usually read these next.

Matter and Materials

Samacheer Kalvi (TN State Board) Class 5 Science — Chapter 2, Matter and Materials. Physical and chemical changes, properties. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

Energy

Samacheer Kalvi (TN State Board) Class 5 Science — Chapter 3, Energy. Forms, sources and conservation of energy. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

Science in Everyday Life

Samacheer Kalvi (TN State Board) Class 5 Science — Chapter 4, Science in Everyday Life. Technology and simple innovations. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

Food

Samacheer Kalvi (TN State Board) Class 5 Science — Chapter 5, Food. Food preservation and balanced nutrition. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.