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Blood and the respiratory system
Blood and the respiratory system

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3 Lung function

Changes in the compliance and resistance of the lungs can affect the capacity of the lungs to hold and exchange air. Lung capacity is calculated from the volume of air that is exchanged during normal and forceful breathing. The volumes that are used to calculate total lung capacity are described in Video 10.

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Transcript: Video 10 Calculating lung capacity.

SPEAKER
Lung capacity is calculated from the volume of air that is exchanged during normal and forceful breathing. Resting tidal volume refers to the amount of air entering or leaving the lungs in a single normal breath, and is about half a litre in adults. 
If you take a deep breath in, the extra volume of air inspired is called the inspiratory reserve volume. Likewise, if you breathe out for as long as you can after a normal intake of breath, the extra volume breathed out is the expiratory reserve volume.
The average inspiratory volume for an adult is about 2 to 3 litres, while the expiratory reserve volume is about 1 litre. There is always a small amount of air left in the lungs in addition to the expiratory reserve volume. And this is known as the residual volume.
Vital capacity is the sum of the tidal, inspiratory and expiratory volumes. Total lung capacity is the sum of all the volumes, including the residual volume. Total lung capacity represents the maximum amount of air that the lungs can hold.
End transcript: Video 10 Calculating lung capacity.
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Video 10 Calculating lung capacity.
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Activity 6 Lung capacity

Timing: Allow about 10 minutes

Part 1

Match the volume with the corresponding definition:

Using the following two lists, match each numbered item with the correct letter.

  1. expiratory reserve volume

  2. inspiratory reserve volume

  3. residual volume

  4. tidal volume

  • a.extra volume breathed in during forceful inhalation

  • b.amount of air entering or leaving the lungs in a single resting breath

  • c.extra volume breathed out during forceful exhalation

  • d.amount of air left in the lungs in addition to the expiratory reserve volume

The correct answers are:
  • 1 = c
  • 2 = a
  • 3 = d
  • 4 = b

a. 

tidal volume


b. 

inspiratory reserve volume


c. 

residual volume


d. 

expiratory reserve volume


The correct answer is c.

c. 

Correct. The vital capacity is the sum of the tidal volume, inspiratory reserve volume and expiratory reserve volume.