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Year 10
Edexcel

The mechanics of breathing

I can explain the mechanics of breathing and how air volumes are measured.

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New
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Year 10
Edexcel

The mechanics of breathing

I can explain the mechanics of breathing and how air volumes are measured.

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Lesson details

Key learning points

  1. During inhalation the intercostal muscles and diaphragm contract to expand the thoracic cavity volume so air rushes in.
  2. During exhalation the intercostal muscles relax, the rib cage returns to its resting position and air is expelled.
  3. A spirometer trace is a graphical representation of lung volume changes over time during breathing.

Keywords

  • Inhalation - the process of breathing in air by expanding the lung volume

  • Exhalation - the process of breathing out air by reducing the lung volume

  • Tidal volume - the volume of air breathed in or out during normal breathing

  • Vital capacity - the maximum amount of air a person can exhale after a maximum inhalation

Common misconception

Tidal volume is the amount of air breathed in and out per breath and the lungs completely empty of air when we expire.

Tidal volume is the volume of air breathed in or out per breadth and it increases during exercise to enable more air and hence exchange of oxygen and carbon dioxide to occur. A residual volume of air always remains in the lungs to keep them inflated.

Check with your science department as they often have a nice visual aid of a glass jar with balloons in it to represent the chest cavity and show how diaphragm movement down helps inflate the lungs due to an increase in volume and hence reduction in pressure withinn the chest (thoracic) cavity.
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Lesson video

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Starter quiz

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6 Questions

Q1.
Where does air enter the body?
the trachea
the alveoli
Correct answer: the nose and mouth
the ears
Q2.
The process of switching oxygen for carbon dioxide is known as exchange.
Correct Answer: gaseous, gas
Q3.
Match the following key terms with the correct description.
Correct Answer:trachea,the windpipe that connects the larynx (voice box) to the bronchi
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the windpipe that connects the larynx (voice box) to the bronchi

Correct Answer:bronchi,two main branches off the trachea that lead to the lungs
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two main branches off the trachea that lead to the lungs

Correct Answer:bronchioles,further subdivisions of bronchi
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further subdivisions of bronchi

Correct Answer:alveoli,tiny air sacs in the lungs where gaseous exchange occurs
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tiny air sacs in the lungs where gaseous exchange occurs

Q4.
Which of the following does not describe the process of diffusion?
particles spreading out
the movement of molecules from higher to lower concentration
gases moving from high to low partial pressure
Correct answer: air being forced out of the body by blowing hard
Q5.
Arrange these body parts in the correct order of inhaled air starting at the atmosphere.
1 - nose and mouth
2 - trachea
3 - bronchi
4 - bronchioles
5 - alveoli
Q6.
Gaseous exchange happens between the and the bloodstream thanks to large capillary networks.
Correct Answer: alveoli, alveolus

Exit quiz

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6 Questions

Q1.
Which of the following terms refers to breathing in?
exhale
expire
perspire
Correct answer: inspire
Q2.
What happens as we breathe in?
Correct answer: the ribs move up and out while the diaphragm flattens down.
the ribs move down and in while the diaphragm flattens down.
the ribs move down and in while the diaphragm moves into a dome.
the ribs move up and out while the diaphragm moves into a dome.
Q3.
Another word for inhale is ...
Correct Answer: inspire, inspiration
Q4.
Match the following key terms with the correct description.
Correct Answer:inspiratory reserve volume,additional air that can be forcefully inhaled after a normal breath in
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additional air that can be forcefully inhaled after a normal breath in

Correct Answer:expiratory reserve volume,additional air that can be exhaled after a normal exhalation
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additional air that can be exhaled after a normal exhalation

Correct Answer:tidal volume,the volume of air breathed in or out during normal breathing
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the volume of air breathed in or out during normal breathing

Correct Answer:vital capacity,maximum amount of air a person can exhale after a maximum inhalation
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maximum amount of air a person can exhale after a maximum inhalation

Correct Answer:residual volume,the volume of air that remains in the lungs after maximal exhalation
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the volume of air that remains in the lungs after maximal exhalation

Correct Answer:minute ventilation,the total volume of gas inhaled or exhaled by the lungs per minute
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the total volume of gas inhaled or exhaled by the lungs per minute

Q5.
Arrange these key processes in the correct order to represent what happens when we breathe in.
1 - the intercostal muscles and diaphragm contract.
2 - the ribs move up and out whilst diaphragm moves down and flattens.
3 - the chest cavity volume increases.
4 - the chest cavity pressure decreases.
5 - air rushes into the lungs from the atmosphere.
6 - gaseous exchange occurs at the alveoli.
Q6.
Match these typical lung volumes with what they are most likely to represent.
Correct Answer:15,number of breaths per minute at rest
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number of breaths per minute at rest

Correct Answer:500 ml,amount of air breathed in at rest per breath (i.e. tidal volume in ml)
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amount of air breathed in at rest per breath (i.e. tidal volume in ml)

Correct Answer:7.5 litres,volume of air breathed in at rest per minute (i.e. minute ventilation)
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volume of air breathed in at rest per minute (i.e. minute ventilation)

Correct Answer:40,example of breathing rate whilst jogging in breaths per minute
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example of breathing rate whilst jogging in breaths per minute

Correct Answer:100 litres,volume of air breathed in during a jog (i.e. minute ventilation)
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volume of air breathed in during a jog (i.e. minute ventilation)