That smoking is dangerous to health is no longer news, neither is it news that smokers are liable to die younger than their non-smoking counterparts. The news is that many people still smoke despite the warnings! With close to 500,000 deaths in its trail every year, the addictive hook of this silent habit is strong!
Smoker's lungs is a descriptive term used to capture the various damaging effects of smoking in the lungs. Unlike healthy lungs with air-filled elastic airbags, a smoker’s lungs are far from healthy, with the lungs losing its elasticity and its capacity to take in air.
Smoker's lungs differ from healthy lungs in several ways. Unlike the elastic tiny airbags that make up healthy lungs, smoker's lungs undergo lots of destructive changes. First, smoking generates thousands of harmful substances called toxins. These toxins get the tiny air-filled elastic bags inflamed. They get swollen, less elastic and eventually form scar tissue. The effects of smoker's lungs can thus be summarized under the broad categories of three conditions namely, chronic obstructive pulmonary disease, emphysema, and chronic bronchitis, which will be explained in simple terms below. 
Tobacco contains nicotine, the addictive chemical, as well as hundreds of harmful substances. Now, the tiny airbags making up the lungs are enriched tiny hairs (cilia) acting as nature's filters, thus protecting us. This is where these harmful substances strike! It destroys the cilia in smoker's lungs, meaning that you breathe in air “hook, line and sinker' with the dirt, the filth and all!
Next, smoking reaches out for the tiny air-filled bags themselves, destroying the bags. The scary bit is that once destroyed, these tiny air-filled bags are not replaceable. It even gets scarier because these air bags play a critical role in delivering oxygen to your body. Now, when so many of these tiny air-filled bags are destroyed, you come down with severe shortness of breath—a disease condition called emphysema.
Next, smoking releases chemicals which go for the kill. The normal activity of one of the cell types in the lungs is mucus production. Produced in the adequate quantity, the mucus produced does the "dirty" job of trapping inhaled irritants and foreign bodies. These foreign bodies only made it to this point because the filtering action of the cilia is lost.
Bearing in mind that the foreign bodies include bacteria, viruses and the likes, the mucus act as one of the protective mechanisms. As a smoker's lungs are constantly being damaged by these toxic chemicals in tobacco, they lose their ability to produce mucus, and then this airway lubrication and protection lost.
To top it up, smoker's lungs are black from years of inhaling injurious chemicals that get scavenged by special cells calked macrophages. Little wonder that coughing up black mucus is common among smokers. Further, it is very common for smokers to suffer from a chronic cough. As smoker's lungs progresses, it isn't uncommon for smokers to experience wheezing and severe shortness of breath. As the tiny air-filled bags lose their elasticity and the tiny branches get filled with dead tissue, low oxygen levels set in with the associated health effects on the lungs and virtually all parts of the body. Over time, the smoker may die of the lung’s inability to take in sufficient amounts of oxygen. 
Take-home message
Smoker's lungs are self-inflicted damage to the lungs, resulting in serious, steady destruction of lung tissues. Little wonder that smokers are liable to die young!
