How Does Cigarette Smoke Affect Alveoli in the Lungs?

alveoli of the lings
Illustration of alveolar sacs in lungs. Science Picture Co/Collection Mix: Subjects/Getty Images

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?

When we inhale, air enters the lungs and travel through passageways to reach 300,000,000 alveoli.

The size of a single alveolus has an approximate diameter of 200-500 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.

The 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). 

Function of Alveoli

Much 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 alveoli and enter the bloodstream via the capillaries. At the same time, carbon dioxide is pushed out in the same way when the 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

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 cigarette additives are radioactive and there is evidence that these chemicals leave permanent radioactive deposits in the smoker's lungs. Researchers believe this is a contributing factor to the risk of ​lung cancer.

Once inhaled, cigarette toxins hitch a ride through your bloodstream 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.

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5 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Encyclopedia Britannica. Pulmonary alveolus.

  3. The Respiratory System. Alveoli.

  4. COPD Foundation. What is COPD?.

  5. Kelley DE, Boynton MH, Noar SM, et al. Effective message elements for disclosures about chemicals in cigarette smoke. Nicotine Tob Res. 2018;20(9):1047-1054. doi:10.1093/ntr/ntx109