Gas exchange between the alveoli and blood (CIE A-level Biology)

This lesson describes the process of gas exchange between air in the alveoli and the blood. The PowerPoint and accompanying worksheet have been designed to cover point 9.1 (d) of the CIE A-level Biology specification

Gas exchange at the alveoli is a topic that was covered at GCSE so this lesson has been written to challenge the recall of that knowledge and to build on it.
The main focus of the lesson is the type of epithelium found lining the alveoli and students will discover that a single layer of flattened cells known as simple, squamous epithelium acts to reduce the diffusion distance.

The following features of the alveolar epithelium are also covered:

Surface area
Moist lining
Production of surfactant
The maintenance of a steep concentration gradient

As a constant ventilation supply is critical for the maintenance of the steep concentration gradient, the final part of the lesson considers the mechanism of ventilation