Breathing

Learn it by playing

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

For educators: ready-to-use lesson slides, revision notes for Breathing (KS3 Science, Biology) — use them in your lesson, or run the topic as an interactive class activity your learners 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.

Air passes from the nasal cavity through the trachea, bronchi and bronchioles to the alveoli; the diaphragm sits below the lungs.

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.

Inhaling increases chest volume as the ribs move up and out and the diaphragm contracts. Exhaling reverses these movements.

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.

Slides

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

Practice questions

Free preview — 8 of 54 questions. Sign up to see them all.

1.Which of the following statements about the diaphragm during inhalation is correct?
Medium
- 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?
Easy
- ABronchioles
- BBronchi
- CAlveoli
- DCapillaries
5.During exhalation, what happens to the volume of the chest cavity?
Easy
- 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?
Medium
- 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

More questions

9.Which muscles contract during inhalation?
Medium
- ADiaphragm only
- BIntercostal muscles only
- CBoth diaphragm and intercostal muscles
- DNeither diaphragm nor intercostal muscles
10.The diagram shows a human respiratory system. Which part is labelled as the trachea?
Easy
- APart A
- BPart B
- CPart C
- DPart D
11.What is the function of the intercostal muscles?
Medium
- ATo change the volume of the chest cavity by moving the ribs
- BTo filter air entering the lungs
- CTo exchange gases in the alveoli
- DTo connect the trachea to the bronchi
12.Which of the following statements is true?
Easy
- AThe lungs are an organ system.
- BThe lungs are an organ.
- CThe lungs are a tissue.
- DThe lungs are a cell.
13.
The table below shows the volume of air in a person's lungs at different times during a breathing cycle. At time 2.0 seconds, the volume is 2.8 dm³. At time 3.0 seconds, the volume is 2.2 dm³. What is the approximate change in lung volume between these two times?
Time (s) Volume of air in lungs (dm³)
2.0 2.8
3.0 2.2
Medium
- A0.6 dm³ decrease
- B0.6 dm³ increase
- C5.0 dm³ decrease
- D5.0 dm³ increase
14.A student measures the air pressure inside a model lung as the diaphragm is pulled downward. The pressure inside the model decreases from 101.3 kPa to 100.5 kPa. The outside air pressure remains at 101.3 kPa. What is the net pressure difference that causes air to flow into the model?
Medium
- A0.8 kPa
- B1.0 kPa
- C101.3 kPa
- D100.5 kPa
15.The diagram shows a bell-jar model of the human breathing system. Which part of the model represents the diaphragm?
Easy
- AA
- BB
- CC
- DD
16.A student uses a spirometer to measure the volume of air inhaled and exhaled during normal breathing. The tidal volume is 0.5 dm³ and the breathing rate is 12 breaths per minute. What is the total volume of air moved into the lungs in one minute?
Medium
- A6.0 dm³
- B0.5 dm³
- C12.0 dm³
- D24.0 dm³
17.During exercise, a person's breathing rate increases from 12 breaths per minute to 24 breaths per minute, and the tidal volume increases from 0.5 dm³ to 1.2 dm³. What is the percentage increase in the volume of air moved per minute?
Hard
- A380%
- B100%
- C140%
- D240%
18.A scientist measures the oxygen concentration in air entering and leaving the lungs. The concentration decreases from 21% to 16%. What does this change indicate?
Medium
- AOxygen is absorbed into the blood
- BCarbon dioxide is released
- CThe air is being warmed
- DWater vapour is added
19.The following statements are about breathing. Which one is true?
Medium
- AGas exchange occurs in the alveoli
- BThe diaphragm relaxes during inhalation
- CThe intercostal muscles contract during exhalation
- DAir moves out of the lungs when chest volume increases
20.Which part of the respiratory system warms and filters the air?
Easy
- ANose
- BTrachea
- CBronchi
- DAlveoli
21.In an experiment, a student uses a model to show how the diaphragm works. She pulls the rubber sheet downward. What happens to the balloons inside the model?
Medium
- AThey inflate
- BThey deflate
- CThey remain unchanged
- DThey pop
22.A patient has a lung disease that reduces the elasticity of the alveoli. How would this affect the process of exhalation?
Hard
- AExhalation becomes more difficult because the lungs cannot recoil properly
- BExhalation becomes easier because the lungs are stiffer
- CThere is no effect on exhalation
- DInhalation becomes more difficult but exhalation is unchanged
23.The diagram shows a cross-section of an alveolus and a surrounding capillary. Which labelled structure is the site of gas exchange?
Easy
- AA
- BB
- CC
- DD
24.Which of the following is the correct order of air passage from the trachea to the alveoli?
Medium
- ATrachea → bronchi → bronchioles → alveoli
- BTrachea → bronchioles → bronchi → alveoli
- CTrachea → alveoli → bronchi → bronchioles
- DTrachea → bronchi → alveoli → bronchioles
25.A student uses a bell-jar model to demonstrate breathing. The rubber sheet at the bottom represents the diaphragm. When the student pulls the rubber sheet downward, what happens to the balloons inside the model?
Medium
- AThey inflate because air pressure inside decreases.
- BThey deflate because air pressure inside increases.
- CThey remain unchanged because the model is sealed.
- DThey inflate because air is pushed into them.
26.A spirometer trace shows tidal volume of 0.5 dm³ and breathing rate of 12 breaths per minute. What is the minute ventilation?
Medium
- A6.0 dm³/min
- B0.5 dm³/min
- C12.5 dm³/min
- D24.0 dm³/min
27.During exercise, a person's breathing rate increases from 12 to 24 breaths per minute and tidal volume increases from 0.5 dm³ to 1.2 dm³. What is the percentage increase in minute ventilation?
Hard
- A380%
- B480%
- C140%
- D240%
28.The diagram shows a model of the respiratory system. Which part represents the trachea? (Diagram: icon_scene with labels: mouth, trachea, bronchi, balloons)
Easy
- AThe tube connecting the mouth to the bronchi
- BThe balloon inside the bell jar
- CThe rubber sheet at the bottom
- DThe glass jar itself
29.In an experiment to measure the effect of exercise on breathing, a student records the number of breaths per minute before and after exercise. Which piece of equipment is most appropriate to measure the volume of each breath?
Medium
- ASpirometer
- BThermometer
- CStethoscope
- DSphygmomanometer
30.A scientist investigates gas exchange by measuring oxygen concentration in inhaled and exhaled air. Inhaled air contains 21% oxygen, exhaled air contains 16% oxygen. What is the percentage of oxygen absorbed by the body?
Medium
- A5%
- B16%
- C21%
- D37%
31.What is the function of the nose in the respiratory system?
Easy
- ATo warm and filter the air
- BTo exchange gases
- CTo produce mucus
- DTo contract and expand the chest
32.A student sets up an experiment to demonstrate the effect of diaphragm movement on lung volume. She uses a bell jar, balloons, and a rubber sheet. Which change would cause the balloons to deflate?
Medium
- APushing the rubber sheet upward
- BPulling the rubber sheet downward
- CRemoving the rubber sheet entirely
- DAdding more balloons
33.The diagram shows a cross-section of an alveolus and a surrounding capillary. Which labelled structure is the site of gas exchange? (Diagram: icon_scene with alveolus and capillary icons, labels: A: alveolus wall, B: capillary wall, C: red blood cell, D: air space)
Medium
- AThe alveolus wall
- BThe capillary wall
- CThe red blood cell
- DThe air space
34.What is the primary function of the nose in the respiratory system?
Easy
- ATo produce sound
- BTo warm and filter the air
- CTo exchange gases
- DTo contract and expand the chest
35.During exhalation, what happens to the diaphragm and intercostal muscles?
Medium
- ABoth contract
- BBoth relax
- CDiaphragm contracts, intercostal muscles relax
- DDiaphragm relaxes, intercostal muscles contract
36.Which sequence correctly describes the path of air from the trachea to the alveoli?
Medium
- ATrachea → bronchioles → bronchi → alveoli
- BTrachea → bronchi → bronchioles → alveoli
- CTrachea → alveoli → bronchi → bronchioles
- DTrachea → bronchioles → alveoli → bronchi
37.The diagram shows a human respiratory system. Which part is labelled as the trachea? (Diagram: icon_scene with labels: mouth, trachea, bronchi, balloons)
Easy
- AA
- BB
- CC
- DD
38.In an experiment to demonstrate breathing, a student uses a bell jar, balloons, and a rubber sheet. Which part of the model represents the diaphragm?
Easy
- AThe bell jar
- BThe balloons
- CThe rubber sheet
- DThe glass tube
39.A student measures the oxygen concentration in inhaled and exhaled air. Inhaled air contains 21% oxygen, exhaled air contains 16% oxygen. What does this change indicate?
Medium
- AOxygen is produced in the lungs
- BOxygen is absorbed into the blood
- COxygen is converted to carbon dioxide
- DOxygen is used to warm the air
40.The diaphragm relaxes during inhalation.
Easy
True or false?
41.The lungs are an organ.
Easy
True or false?
42.The intercostal muscles relax during exhalation.
Easy
True or false?
43.Gas exchange takes place in alveoli.
Easy
True or false?
44.Expanding the chest cavity causes a reduction in pressure.
Medium
True or false?
45.The nose filters air and traps dust and other particles.
Easy
True or false?
46.The trachea contracts during inhalation.
Easy
True or false?
47.Match each part of the respiratory system with its function.
Medium
- Nose
- Trachea
- Alveoli
- Diaphragm
- Filters and warms air
- Connects throat to lungs
- Site of gas exchange
- Muscle that changes chest volume
48.Put the following events of inhalation in the correct order.
Medium
- Diaphragm contracts and moves downward
- Chest cavity volume increases
- Air pressure inside lungs decreases
- Air is drawn into lungs
49.Which of the following statements about exhalation are correct? (Select all that apply.)
Hard
- AThe diaphragm relaxes
- BThe intercostal muscles contract
- CChest cavity volume decreases
- DAir pressure inside lungs increases
- EAir moves out of the lungs
50.Describe what is meant by breathing.
Easy
51.Describe how air reaches the alveoli from the trachea.
Medium
52.Describe the role of the diaphragm and intercostal muscles in inhalation.
Medium
53.Explain why the pressure inside the lungs changes during inhalation and exhalation and how this affects air movement.
Hard
54.What is the name of the large muscle below the lungs that helps with breathing?
Easy

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 54 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

Time (s)	Volume of air in lungs (dm³)
2.0	2.8
3.0	2.2