The respiratory menbrane lining the air sacs consist of what?

Question

The actual site of gas exchange within the lungs are?

the actual site of gas exchange in the lungs are at the capillaries (smallest blood vessels)

You are talking about the alveoli. Since this is not my area of expertise, I searched Google under the key words "alveoli" to get these possible sources:

http://oac.med.jhmi.edu/res_phys/Encyclopedia/Alveoli/Alveoli.HTML
http://en.wikipedia.org/wiki/Alveoli
http://www.sk.lung.ca/content.cfm?edit_realword=alveoli
http://lungdiseases.about.com/od/glossaryofterms/g/alveoli.htm
http://science.nhmccd.edu/biol/respiratory/alveoli.htm

I hope this helps a little more. Thanks for asking.

The area of the cerebral cortex that allows understanding and interpretation of somatic sensory information