Human Body: The Organ Systems

A Today you'll learn

Understand what organs and organ systems are in the human body
Describe the roles of the skeletal, muscular, digestive, respiratory, and circulatory systems
Recognise key internal organs: brain, heart, lungs, stomach, and kidneys

B Let's understand

The human body is like an extraordinary machine. It is built from tiny cells that form tissues, tissues that form organs, and groups of organs that work together as organ systems. The skeletal system is made of 206 bones that give our body shape and protect delicate internal organs like the brain and heart. The muscular system works with bones to help us move. The respiratory system (nose, windpipe, lungs) takes in oxygen and removes carbon dioxide. The circulatory system, powered by the beating heart, pumps blood carrying oxygen and nutrients to every part of the body. The digestive system breaks down food so our body can absorb energy, while the nervous system (brain and nerves) controls all our thoughts and actions.

C See it step by step

Example 1: Which organ system protects our brain and heart?

The skeletal system protects our vital internal organs.
The skull (cranium) protects the delicate brain.
The ribcage protects the heart and lungs.

Example 2: Trace the path of air when you take a breath.

Air enters through the nose or mouth, where tiny hairs filter dust.
It travels down the windpipe (trachea).
It reaches the two lungs, where oxygen passes into the blood and carbon dioxide is removed.

D Your turn

Which organ acts as the master control centre of the body?

Look back at "Let's understand" above for a clue.

E Ready to practise?

Key idea 1

An organ system is a group of organs working together to perform a major body job.

Key idea 2

The skeletal system (206 bones) provides structure, support, and organ protection.

Key idea 3

The heart pumps blood through blood vessels across the entire body (circulatory system).

Key idea 4

The lungs take in oxygen and breathe out carbon dioxide (respiratory system).

Key idea 5

The brain is the control centre of the body, directing thoughts, senses, and movements.

Warm up

1. How many bones make up an adult human skeleton?

2. Which organ pumps blood throughout the body?

3. Name the organ system responsible for breaking down food.

Practise

4. Which organ controls all the functions of the body and thinking?

5. What two major organs are protected by the ribcage?

6. What gas do our lungs absorb from the air we inhale?

Challenge

7. Name the pair of bean-shaped organs that filter waste from our blood.

8. How do muscles and bones work together when you bend your arm?

Download worksheet (PDF)

Question 1: How many bones make up an adult human skeleton?

Answer: 206 bones.

Question 2: Which organ pumps blood throughout the body?

Answer: The heart.

Question 3: Name the organ system responsible for breaking down food.

Answer: Digestive system.

Question 4: Which organ controls all the functions of the body and thinking?

Answer: The brain.

Question 5: What two major organs are protected by the ribcage?

Answer: The heart and the lungs.

Question 6: What gas do our lungs absorb from the air we inhale?

Answer: Oxygen.

Question 7: Name the pair of bean-shaped organs that filter waste from our blood.

Answer: Kidneys.

Question 8: How do muscles and bones work together when you bend your arm?

Answer: Muscles contract (pull) on bones at joints to cause movement; muscles always pull and never push.