Gaseous Exchange in Mammals and Breathing

Syllabus tag: KCSE | Biology | Form 2 | Topic 3 Gaseous Exchange

Lesson objectives

By the end of this topic, you should be able to:

• Describe the structure of the mammalian respiratory system.
• Explain the mechanism of inspiration and expiration.
• Describe gaseous exchange at the alveolus and the transport of gases.
• Explain the control of breathing and the effects of smoking.

Summary

Air reaches the lungs through the trachea, bronchi and bronchioles, ending in millions of alveoli where exchange occurs. Breathing is brought about by the diaphragm and intercostal muscles changing the volume of the thorax: greater volume means lower pressure, so air rushes in. Breathing rate is controlled by carbon dioxide, not oxygen.