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The Respiratory System

Gaseous exchange at the alveoli and muscles

  • 3 things to know
  • A2 2

Overview

Partial pressure, external and internal respiration, oxygen and carbon dioxide movement, alveolar adaptations, Fick's law, blood flow and ventilation, training effects and smoking damage.

What you need to know

Answer each one before you reveal it.

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Key term

What is gaseous exchange?

Key term

What is partial pressure?

Key term

What is external respiration?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is gaseous exchange?

    Model answer

    Gaseous exchange is the movement of oxygen and carbon dioxide between the air, the blood and the tissues by diffusion. Each gas moves from a high to a low partial pressure.

  2. 2

    What is partial pressure?

    Model answer

    Partial pressure is the pressure exerted by one gas within a mixture of gases. The difference in partial pressure between two areas drives diffusion.

  3. 3

    What is external respiration?

    Model answer

    External respiration is gas exchange between the alveoli and the blood in the pulmonary capillaries. Oxygen moves into the blood and carbon dioxide moves out.

  4. 4

    What is internal respiration?

    Model answer

    Internal respiration is gas exchange between the capillary blood and the muscle cells. Oxygen moves into the muscle and carbon dioxide moves into the blood.

  5. 5

    Explain the movement of oxygen at the alveoli using partial pressures.

    Model answer

    Alveolar air has a partial pressure of oxygen of about 100 mmHg (13.3 kPa). Blood arriving at the lungs is about 40 mmHg (5.3 kPa), so oxygen diffuses into the blood.

  6. 6

    Explain the movement of carbon dioxide at the alveoli using partial pressures.

    Model answer

    Blood arriving at the lungs has a partial pressure of CO₂ of about 45 mmHg (6.0 kPa). Alveolar air is about 40 mmHg (5.3 kPa), so CO₂ diffuses into the alveoli.

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AThe target heart rate is about 168 bpm.
BMaximum heart rate is 220 − 18 = 202 bpm.
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Inspiration means breathing air into the lungs.
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