Using the 40X objective, carefully examine walls of alveoli.

• Identify macrophages (dust cells),
• The flattened type I pneumocytes, and
• The rounded type II pneumocytes.
• Not many nuclei of type I cells will be visible. Why?

What is the major chemical property of surfactant?

Compare and contrast type I and type II pneumocytes.
 

Now comes the urinary system.