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The Respiratory System

The mechanics of breathing

  • 3 things to know
  • Component 1

Overview

Pulmonary ventilation, the diaphragm and external intercostals in inspiration, the extra muscles used in exercise, passive and active expiration, thoracic volume and pressure, pressure gradients, the control of breathing in exercise and the warm-up.

What you need to know

Answer each one before you reveal it.

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Key term

Why does air move into and out of the lungs?

Key term

Define pulmonary ventilation.

Key term

Which muscles contract to produce inspiration at rest?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define pulmonary ventilation.

    Model answer

    Pulmonary ventilation is the movement of air into and out of the lungs. Inspiration draws air in and expiration moves air out.

  2. 2

    Which muscles contract to produce inspiration at rest?

    Model answer

    The diaphragm and the external intercostal muscles contract during inspiration at rest.

  3. 3

    What does the diaphragm do during inspiration?

    Model answer

    The diaphragm contracts and flattens, moving downwards. The thoracic cavity becomes longer from top to bottom.

  4. 4

    What do the external intercostals do during inspiration?

    Model answer

    The external intercostals pull the ribs upwards and outwards. The thoracic cavity widens from front to back and side to side.

  5. 5

    Explain the cause and effect of air entering the lungs during inspiration.

    Model answer

    The volume of the thoracic cavity increases, so the pressure inside the lungs falls below atmospheric pressure. Air flows down the pressure gradient into the lungs.

  6. 6

    Which additional muscles assist inspiration during exercise?

    Model answer

    The sternocleidomastoid and pectoralis minor lift the sternum and ribs higher. The thoracic cavity expands further, so more air is drawn in.

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