What Alveoli Are and How Cigarettes Destroy Them

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Illustration of alveolar sacs in lungs - closeup. Science Picture Co/Collection Mix: Subjects/Getty Images

What are Alveoli?

Alveoli (singular is alveolus) are tiny, delicate air sacs deep within the lungs. They look like little clusters of grapes at the ends of the bronchial branches in the lungs.

How Many Alveoli are in the Lungs and How Big Are They?

Researchers looking at six sets of adult human lungs found that the number of alveoli contained within averaged 480 million, ranging from 274 million on the low end to 790 million on the high end.

The number of alveoli did relate to the overall size of the lungs studied.

The size of a single alveolus has the approximate diameter of 200 microns, regardless of lung size. As a point of reference, one micron is a millionth of a meter. The diameter of a human hair is about 70 microns, so one alveolus would be close to equal the diameter of three human hairs put together. Tiny!

Alveoli contain collagen and elastin.  Collagen offers firmness to the air sac structure and elastin, bounce. When air is inhaled into the lungs, elastin allows alveoli to expand, and upon exhalation, spring back to their original size.

Total surface area of all alveoli in a healthy adult set of lungs is approximately 70 square meters, or 800 square feet (approximately the size of half a tennis court). 

What is the Function of Alveoli?

Upwards of 70 percent of the outside surface area of lung alveoli are covered with tiny capillaries.

These capillaries and the walls of alveoli share a very thin membrane that allows oxygen from inhaled air to pass through the walls of aveoli and enter the bloodstream via the capillaries.  At the same time, carbon dioxide is pushed out in the same way when air is exhaled.

The total amount of surface area available for this gas/blood exchange determines how well a person is able to breathe.

In a normal healthy adult, there is an abundance of available area for this process.

Cigarette Smoking and Alveoli

Over time, the toxins from inhaled cigarette smoke break the thin walls of alveoli, leaving larger, less efficient air sacs. The sacs also begin to lose their bounce, making it harder to bring in the oxygen and expel carbon dioxide. Both can become partially trapped in the lungs.   In a smoker, this process signals the beginning of emphysema, a form of COPD. 

The damage from emphysema cannot be reversed.  Once air sacs are broken, they do not mend. However, if exposure to cigarette smoke stops soon enough, the damage can be halted.  If smoking continues, there will come a point where lung damage will progress regardless of whether a person stops smoking or not.

Good Reasons to Stop Smoking Now

The lesson here is to stop smoking as soon as you possibly can. Every cigarette you smoke is hurting your body in numerous ways. Cigarette smoke is chock full of chemicals that cause cancer and are poisonous.

 Some are even radioactive, and there is evidence that they leave permanent radioactive deposits in smoker's lungs. Researchers believe this is a contributing  factor for the risk of lung cancer.

Once inhaled, cigarette toxins hitch a ride through your blood stream via the alveoli where they have access to every organ in your body. It's no wonder that cigarette use is linked to so many diseases.

There is nothing to recommend smoking.   We think we enjoy it, but it's an addiction, plain and simple.

Quit smoking now using the links below. 

An Educated Quit is a Successful Quit

How to Develop Strong Quit Muscles

10 Tips That Helped Me Quit - Leo's Story

Sources:

National Institutes of Health. The Number of Alveoli in the Human Lung. http://www.ncbi.nlm.nih.gov/pubmed/14512270.  September 25, 2003.

National Institutes of Health. National Heart, Lung and Blood Institute. The Respiratory System. http://www.nhlbi.nih.gov/health/health-topics/topics/hlw/system. Updated July 17, 2012.

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