Concept:Smoking destroys the cilia lining the respiratory tract, impairing the body's ability to clear mucus and pathogens.
Explanation:Cilia are tiny hair-like structures that line the respiratory tract and move in a rhythmic wave-like motion to sweep mucus, dust, and pathogens out of the lungs.
Tobacco smoke contains toxic chemicals such as tar and nicotine, which act as irritants to the respiratory lining.
The primary effect observed is the destruction of cilia, particularly in the upper respiratory tract, which includes the trachea and bronchi.
This destruction is often preceded by ciliostasis, the paralysis of cilia.
When cilia are destroyed or paralyzed, the mucociliary escalator fails, causing mucus and debris to accumulate in the airways.
This leads to a persistent smoker's cough and an increased risk of respiratory infections.
Options suggesting the promotion of cilia are incorrect because tobacco chemicals are cytotoxic and inhibit cellular function rather than stimulating growth.
Although the lower respiratory tract is also affected, such as damage to alveoli leading to emphysema, the loss of the ciliary defense mechanism is most prominently noted in the upper conducting passages.
Additionally, smoking reduces the blood's oxygen-carrying capacity because carbon monoxide (
CO) binds to hemoglobin (
Hb) more strongly than oxygen (
O2​), forming carboxyhemoglobin.
Long-term smoking also increases the risk of chronic bronchitis and lung cancer due to the presence of carcinogens in tobacco.
Answer:B. Destruction of cilia in upper respiratory tract