As Exchange-Structure and function of Alveoli

Please do not make it more than 1100 words. Becoz last essay i had received form other writer was 1600 words and I asked for 1000 words. So please take that into consideration. It is actually an essay of anatomy and physiology. following is the description and example of essay type:

Relate the Structure to the functioning of a body system particularly those involved in gas exchange and transport.

An Example of relating structure to function: The structure of the kidneys (proximal & distal tubule, Loop of Henle, collecting duct and all associated vasculature) is perfectly designed to achieve its function of processing, filtering, and conditioning the bood plasma and ultimately produce urine. It does this by…………………….

In my topic please discuss, how alveoli is involved in gas exchange and respiratory system both anatomy and function.

1000 Word Essay
Single Sided, Double spaced, One inch Margins, 12 Font
No citations-but produce a list of at least 4 references. APA format.

only the refernces needs to be in APA style not the entire essay. you can use MLA for the paper and APA for refernces.

Thank you.