Science & Technology in Action

1st Edition

The Science of Breathing

Teva Ireland

Jnr Science Cert
The human respiratory system is the subject of this lesson. The function of the lungs in inspiration and expiration is described. The concepts of breathing and respiration are contrasted. The mechanics of gas exchange with the blood are also described.
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Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

Why do we need to breathe?
This lesson provides an overview of the respiratory system. In particular it focuses on the physical aspects of breathing, and the importance of gas exchange for respiration and life.

We need oxygen to live. When we breathe in, oxygen travels in the air through the trachea and bronchi, into the bronchioles and finally reaches numerous sac-like structures called alveoli. The thin surfaces of the alveoli are in contact with blood vessels calledcapillaries. At the alveoli, oxygen enters the blood to be carried to cells in the body. Waste carbon dioxide in the blood is excretedat the alveoli and expelled in the air we breathe out.

What is the Irish connection with breathing?
Robert Boyle (1627 – 1691), the Irish chemist showed that a change in the volume of a fixed mass of gas causes a change in pressure. If the gas volume increases the pressure decreases and vice versa.

When the air in the lungs expands, its pressure decreases to less than atmospheric pressure. But its pressure rises above atmospheric pressure when it is compressed.

Air moves from higher to lower pressure until the air pressures are equal. Therefore by creating a pressure difference, air can be moved into and out of the lungs.

True or False?

  1. Respiration releases energy. true
  2. Aerobic respiration releases less energy than fermentation. false
  3. The same amount of CO2 is made as oxygen is used in respiration. true
  4. Urea is made and excreted by the liver. true
  5. Gas exchange occurs at the alveoli. true
  6. Gas exchange occurs by osmosis. false
  7. The alveoli are surrounded by blood capillaries. true
  8. Air flows from higher to lower pressure. true
  9. Contraction of the diaphragm and intercostal muscles brings in air. true
  10. The intercostal muscles are responsible for most of the airflow. false
  11. The collapse of the lungs is due to their elastic recoil. true
  12. The average relaxed breathing rate is 30 breaths a minute. false