The Student Room Group

What is required to know for AQA Bio gas exchange in mammals?

Do I need to know the adaptations and roles of the trachea and bronchi?

On the specification it says "The gross structure of the human gas exchange system limited to
the alveoli, bronchioles, bronchi, trachea and lungs.
The essential features of the alveolar epithelium as a surface over
which gas exchange takes place.
Ventilation and the exchange of gases in the lungs. The
mechanism of breathing to include the role of the diaphragm and
the antagonistic interaction between the external and internal
intercostal muscles in bringing about pressure changes in the
thoracic cavity."

But on Freesciencelessons and physicsandmathstutor they all mention stuff like goblet cells, and cartilage lining the trachea.
Hi you need to understand basic concepts RE: trachea i.e. that it:-
a] has cartilage rings so that it does not collapse with -ve pressure created during inspiration [due to expansion of chest brought about by contraction of the diaphragm and external intercostal muscles].
b] has cilia on its mucosal inne r layer and mucus secreted by the goblet cells, both of which jointly prevent entrry of debris or pathogens into the lower respiratory tract.

The same applies to the larger bronchi; however, you do not need any more intricate detail at A level

Also make sure you understand fully the super efficiency of gas exchange effected by:


Huge no of minute alveoli that have surface area of a tennis court in just one lung


Alveolar wall and capillary endothelium [each only one cell thick so just a few microns] means O2 has to diffuse thru only v short distance.


The faCT THAT THE DIAMETER of the erythrocyte [red blood cell] is about the same [7 microns] as the diameter of the capillary so red cells just squeeze thru hence allowing time for gas exchange.

Work out things logically by thinking and you will excel!

Good luck"!



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