A lot of people are aware of the fact that smoking cigarettes can lead to death in many forms. It is well known that smokers have an increased risk for heart disease, cancer, and other lung diseases such as COPD. A lot of people are also aware of the damage smoking does to your lungs over time, with some studies showing that around 70% of the total health costs from smoking come from damage done to your lungs after the first couple years (1).
comparing between the healthy lungs and smoker's lungs:
Visible differences between the healthy lungs and smokers lungs are mainly seen in the alveoli, which are the sacs located in your lungs which hold oxygen and help it travel through your body. Healthy alveoli are usually spherical in shape and pink, with an elastic appearance. Although there are still two types of cells that make up alveoli, healthy alveoli contain mostly small type I pneumocytes. These small type 1 pneumocytes help to make up a barrier that protects your lungs from outside invaders such as bacteria or viruses (2). The other type of cell found in alveoli is the larger type 2 pneumocyte. It is designed to produce surfactant. Surfactant, also known as surfactant activity, is a thin chemical that protects your lungs from things like dust, and helps to clean up after you have inhaled a foreign particle (3). Your alveoli are lined with type II pneumocytes which are in turn lined with type IV pneumocytes. Alveolar macrophages make up another type of cell found in the alveoli. The macrophages around your alveoli play a vital role in lung health. A healthy macrophage is able to kill off certain types of bacteria and virus (2). A healthy macrophage also secretes a type of molecule called interleukin-1beta (IL-1beta), which has the ability to turn off many types of inflammatory chemicals, like cytokines (4). For example, IL-1beta targets NK cells, T cells, and eosinophils (4).
The type 3 pneumocyte commonly found in healthy alveoli is also known as an epithelial cell. Type 3 pneumocytes are different from other type 1 and type 2 cells because they are not only transdifferentiated into a different cell type. However they retain the ability to produce surfactant. The epithelial cells lining your alveoli form alveolar walls in which you can breathe. These cells are very similar to the type 1 pneumocytes and type 2 pneumocytes (2). The epithelial cells along with the macrophages and alveolar cells help keep your lungs protected from outside invaders.
As for a smokers lungs, smokers have a much harder time with their lung health. A large number of smokers develop COPD, or chronic obstructive pulmonary disease (5). COPD is a condition that makes it hard for you to breathe. Smokers develop COPD when the airways and alveoli become inflamed and usually covered with mucus (6). These symptoms are usually brought on by smoking cigarettes, but can also be found in people who smoke marijuana or other types of drugs. The severity of COPD can vary from person to person, but it usually gets worse as time goes by. For example, many smokers begin to develop COPD after smoking a pack of cigarettes every day for ten years (5).
The lungs in a smoker contain many mucus producing cells. These mucus creating cells are called goblet cells, but they are also sometimes referred to as pseudostratified columnar epithelial cells (PCCs) and Clara Cells. Although PCCs and Clara Cells have the same functions in healthy lungs, they usually look very different than each other in smokers. PCCs and Clara Cells create mucus because they are lined with cilia. Cilia are designed to help you clean the mucus out of your lungs. However, in a smoker these cilia-lined cells seem to be less effective at this job (7). As a cigarette continues to burn it usually creates hundreds of chemicals, and these chemicals can irritate your PCCs and Clara's. Irritation of these cells causes them to become inflamed, which can lead to the creation of more mucus (8). The goblet cells then produce more mucus in order to protect themselves from inflammation in the adjacent tissues (9). Unfortunately, this cycle of inflammation will continue as long as you are smoking cigarettes. This is one of the main factors that lead to COPD.
The respiratory bronchioles are also affected to some extent in a smoker. Because smokers tend to have mucus lining in their alveoli and bronchioles, they usually become inflamed over time as well (10). This inflammation of the bronchioles will make it harder for you to breathe, which is why it leads to COPD. It is important for the bronchioles to stay clear of mucus because they are where oxygen enters your body from the air outside of your body. If the airway becomes blocked by mucus, oxygen cannot get into your blood stream. That is why smokers will often develop infections such as pneumonia. Pneumonia is an infection of your lungs that usually enters your lungs and causes further inflammation. Although a lot of people who smoke cigarettes get pneumonia, people who smoke marijuana or other types of drugs also develop pneumonia (11).
The last place you will commonly find mucus and inflammation in the lungs of a smoker occurs in the small air sacs called alveoli. Alveoli are responsible for allowing oxygen to get into your blood stream, so they are very important to overall lung health (12). Many diseases of the lungs caused by smoking affect the alveoli.
Because smokers often have inflammation in their bronchioles, this usually means that the alveoli are also inflamed. As mentioned earlier, inflammation in alveoli is a major factor in COPD (13). It will tend to get worse as you continue to smoke cigarettes over time. Cigarettes contain many chemicals that enter your lungs and cause your alveoli to become inflamed. These chemicals can cause problems with the immune system of your body and they can also irritate the cells within your lungs (14). Symptoms such as persistent cough or a low fever can be caused by inflammation of your alveoli (15). There are many genes that can trigger the inflammation of your alveoli. One of these genes is called the cytokine gene, and a specific type of cytokine called interleukin-1beta (IL-1beta) can cause lung problems as well (16). IL-1beta is a type of molecule that is secreted by alveolar macrophages. Many scientists believe that IL-1beta causes your alveoli to become inflamed (17). So, in summary, although there are many different issues in the lungs of a smoker, it all comes down to inflammation in the air sacs called alveoli.
