CIE A Level Biology (9700) 2019-2021

Revision Notes

9.1.5 Structures & Functions of the Gas Exchange System

The Gas Exchange System: Structure & Functions

  • Ciliated epithelial cells, goblet cells and mucous glands play vital roles in maintaining the health of the gas exchange system
  • Cartilage, smooth muscle, elastic fibres and squamous epithelial tissue all play important structural roles in maintaining the gas exchange system

Structures & functions in the gas exchange system table

Structures & Functions in the Gas Exchange System Table, downloadable AS & A Level Biology revision notes

Worked example: Effect of cystic fibrosis on lung function

Describe the cause of cystic fibrosis and explain how cystic fibrosis affects the function of the lungs

Cystic fibrosis is caused by a recessive allele of the CFTR gene. Cystic fibrosis affects the lungs by goblet cells producing thick, sticky and dehydrated mucus. This mucus is much harder for cilia to sweep up the trachea and to the mouth and so mucus accumulates in the airways. As the mucus traps bacteria but the mucus can’t be removed, this leads to frequent infections and eventually scar tissue in the lungs. The fact that mucus obstructs the airways means that gas exchange is less efficient as it is harder for oxygen to reach the lungs and harder for carbon dioxide to be exhaled, causing breathing problems.

Exam Tip

Make sure that you don’t confuse the cilia in the respiratory system for microvilli in the small intestine. At first glance they appear similar, but they have very different functions! Cilia are for sweeping mucus while microvilli are for the absorption of nutrients.

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