Smoking has profound and damaging effects on the respiratory tract, particularly on the mucous membranes that line the airways. These membranes, which include the epithelial lining of the nose, throat, trachea, bronchi, and lungs, are crucial in protecting the respiratory system from infections, pollutants, and irritants. The harmful chemicals in cigarette smoke—such as nicotine, tar, carbon monoxide, and formaldehyde—cause both immediate and long-term damage to these membranes.<br />-Irritation and Inflammation :Cigarette smoke contains thousands of harmful chemicals that directly irritate the respiratory tract. This irritation leads to: Redness and swelling of the mucous membrane,Increased mucus production as the body tries to trap and expel harmful particles and Chronic inflammation, which damages the cells lining the airways over time.<br />- Damage to Cilia :The respiratory tract is lined with tiny, hair-like structures called cilia, which help move mucus and trapped particles out of the lungs. Smoking leads to Paralysis of cilia, preventing them from clearing mucus and debris,Increased mucus buildup, which can cause chronic cough (commonly known as "smoker's cough") andHigher risk of respiratory infections such as bronchitis and pneumonia due to impaired clearance of pathogens.<br />- Structural Changes to the Epithelium :Long-term smoking causes the normal, ciliated columnar epithelium in the respiratory tract to be replaced by squamous epithelium, a process known as squamous metaplasia. This change:Reduces the protective function of the lining,Increases the risk of cancerous transformations and Leads to conditions like chronic bronchitis and chronic obstructive pulmonary disease (COPD).<br />- Increased Susceptibility to Infections :Because smoking weakens the respiratory defenses, smokers are more likely to develop:Bacterial and viral infections, such as influenza and tuberculosis and Chronic respiratory diseases, including chronic bronchitis and emphysema.<br /><br />AL_mustaqbal University is the first university in Iraq<br />