Breathing

Learn it by playing

Answer these questions to earn energy, then fish and explore. No account needed.

For teachers: ready-to-use lesson slides, revision notes, diagrams for Breathing (KS3 Science, Biology) — use them in your lesson, or run the topic as an interactive class activity your students play as a live game.

Lesson notes

The Respiratory System

**Breathing** is the mechanical process that moves air in and out of the lungs.
The **respiratory system** includes the nose, mouth, trachea, lungs, and diaphragm.
The **nose** warms and filters air, trapping dust and particles.
The **trachea** (windpipe) connects the throat to the lungs.
The trachea divides into two **bronchi** (one per lung), which split into smaller **bronchioles**.
Bronchioles lead to tiny air sacs called **alveoli**, where gas exchange occurs.
The **diaphragm** is a large muscle below the lungs that contracts and relaxes to change chest volume.

Inhalation (Breathing In)

The **diaphragm contracts** and moves downward, increasing chest cavity volume.
**Intercostal muscles** contract, pulling the ribcage up and out.
Increased chest volume **lowers air pressure** inside the lungs relative to outside.
Air is drawn in through the nose/mouth, down the trachea and bronchi, into the alveoli.

Exhalation (Breathing Out)

The **diaphragm relaxes** and moves upward, decreasing chest cavity volume.
**Intercostal muscles** relax, allowing the ribcage to move down and in.
Decreased chest volume **raises air pressure** inside the lungs.
Higher pressure forces air out of the alveoli, up the bronchi and trachea, and out through the nose/mouth.

Key Points

The lungs are an **organ** of the respiratory system.
Gas exchange occurs in the **alveoli**.
Inhalation: diaphragm contracts, chest volume increases, pressure decreases, air flows in.
Exhalation: diaphragm relaxes, chest volume decreases, pressure increases, air flows out.
The **nose filters air** and traps dust and particles.

The respiratory system showing the nose, trachea, lungs, and diaphragm.

Slides

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

Practice questions

Free preview — 8 of 40 questions. Sign up to see them all.

1.Which of the following statements about the diaphragm during inhalation is correct?
Easy
- AThe diaphragm relaxes and moves upward.
- BThe diaphragm contracts and moves downward.
- CThe diaphragm relaxes and moves downward.
- DThe diaphragm contracts and moves upward.
2.Which of the following is NOT part of the respiratory system?
Easy
- ATrachea
- BLungs
- CDiaphragm
- DOesophagus
3.What is the main function of the nose in the respiratory system?
Easy
- ATo warm and filter the air
- BTo exchange gases
- CTo produce mucus
- DTo connect the throat to the lungs
4.The trachea divides into two tubes. What are these tubes called?
Medium
- ABronchioles
- BBronchi
- CAlveoli
- DCapillaries
5.During exhalation, what happens to the volume of the chest cavity?
Medium
- AIt increases
- BIt decreases
- CIt stays the same
- DIt fluctuates rapidly
6.Which of the following sequences correctly describes the path of air from the trachea to the alveoli?
Hard
- ATrachea → bronchioles → bronchi → alveoli
- BTrachea → bronchi → bronchioles → alveoli
- CTrachea → alveoli → bronchi → bronchioles
- DTrachea → bronchioles → alveoli → bronchi
7.Gas exchange occurs in which part of the respiratory system?
Easy
- ATrachea
- BBronchi
- CAlveoli
- DDiaphragm
8.What causes air to move into the lungs during inhalation?
Medium
- AHigher pressure inside the lungs than outside
- BLower pressure inside the lungs than outside
- CEqual pressure inside and outside the lungs
- DThe diaphragm relaxing

Revision notes

## Breathing Revision Notes ### What is Breathing? Breathing is the **mechanical process** that moves air in and out of the lungs, allowing us to take in oxygen and expel carbon dioxide. ### The Respiratory System Includes: nose, mouth, trachea, lungs, diaphragm. - **Nose and mouth**: Air enters; nose warms and filters air, trapping dust. - **Trachea** (windpipe): Connects throat to lungs. - **Lungs**: Trachea divides into **bronchi** (one per lung), which split into **bronchioles**, leading to **alveoli** (air sacs where gas exchange occurs). - **Diaphragm**: Large muscle below lungs; contracts/relaxes to change chest volume. ### Inhalation (breathing in) 1. Diaphragm **contracts** and moves **downward**. 2. Intercostal muscles **contract**, pulling ribcage **up and out**. 3. Chest cavity volume **increases** → pressure inside lungs **decreases** (lower than outside). 4. Air is drawn **in** through nose/mouth → trachea → bronchi → alveoli. ### Exhalation (breathing out) 1. Diaphragm and intercostal muscles **relax**. 2. Chest cavity volume **decreases** → pressure inside lungs **increases** (higher than outside). 3. Air is forced **out** of alveoli → bronchi → trachea → nose/mouth. ### Key Points - Gas exchange occurs in **alveoli**. - Breathing is **mechanical** (not gas exchange itself). - Pressure changes drive air movement: lower pressure inside draws air in; higher pressure pushes air out.

Breathing: The mechanical process that moves air in and out of the lungs, allowing us to take in oxygen and expel carbon dioxide.
Respiratory system: Organ system including the nose, mouth, trachea, lungs, and diaphragm.
Trachea: Also known as the windpipe; connects the throat to the lungs.
Bronchi: Two tubes that the trachea divides into, one for each lung.
Bronchioles: Smaller tubes that bronchi split into, leading to alveoli.
Alveoli: Small air sacs in the lungs where gas exchange takes place.
Diaphragm: A large muscle located below the lungs that contracts and relaxes to change the volume of the chest cavity.
Intercostal muscles: Muscles between the ribs that contract and relax to move the ribcage during breathing.
Inhalation: The phase of breathing when air is drawn into the lungs; diaphragm and intercostal muscles contract, increasing chest volume and lowering pressure.
Exhalation: The phase of breathing when air is forced out of the lungs; diaphragm and intercostal muscles relax, decreasing chest volume and raising pressure.

Flashcards

What is breathing?

Breathing is the mechanical process that moves air in and out of the lungs, allowing us to take in oxygen and expel carbon dioxide.

What organ system do the lungs belong to?

The lungs are part of the respiratory system.

List the main parts of the respiratory system.

Nose, mouth, trachea, lungs, and diaphragm.

What is the function of the nose in the respiratory system?

The nose warms and filters the air, trapping dust and other particles.

What is another name for the trachea?

The trachea is also known as the windpipe.

What are the two tubes called that the trachea divides into?

The trachea divides into two tubes called bronchi, one for each lung.

What are the smaller tubes that bronchi split into?

The bronchi split into smaller tubes called bronchioles.

Where does gas exchange take place in the lungs?

Gas exchange takes place in the alveoli, which are small air sacs.

What is the diaphragm?

The diaphragm is a large muscle located below the lungs that contracts and relaxes to change the volume of the chest cavity.

What are the two phases of breathing?

Inhalation (breathing in) and exhalation (breathing out).

What happens to the diaphragm during inhalation?

During inhalation, the diaphragm contracts and moves downward.

What happens to the intercostal muscles during inhalation?

During inhalation, the intercostal muscles contract and pull the ribcage up and out.

How does the chest cavity volume change during inhalation?

During inhalation, the chest cavity volume increases.

What happens to air pressure inside the lungs during inhalation?

The increase in chest cavity volume lowers the air pressure inside the lungs compared to outside.

Why does air flow into the lungs during inhalation?

Air is drawn in because the pressure inside the lungs is lower than outside the body.

What happens to the diaphragm during exhalation?

During exhalation, the diaphragm relaxes.

What happens to the intercostal muscles during exhalation?

During exhalation, the intercostal muscles relax.

How does chest cavity volume change during exhalation?

During exhalation, the chest cavity volume decreases.

What happens to air pressure inside the lungs during exhalation?

The decrease in chest cavity volume raises the air pressure inside the lungs.

Why does air flow out of the lungs during exhalation?

The higher pressure inside the lungs forces air out of the alveoli and out through the nose or mouth.

True or false: The diaphragm relaxes during inhalation.

False. The diaphragm contracts during inhalation.

True or false: The intercostal muscles relax during exhalation.

True.

True or false: Gas exchange takes place in alveoli.

True.

True or false: Expanding the chest cavity causes a reduction in pressure.

True.

Describe how air reaches the alveoli from the trachea.

Air goes from the trachea into the bronchi, then into smaller bronchioles, and finally into the alveoli.

Unlock all 40 questions, flashcards & more

Create a free account to see every question, the slides, flashcards and revision notes for this topic.

Past papers

Past-paper practice for this topic is coming soon.

Coming soon