Free Human Respiratory System MCQs with Answers

31. Damage to the cilia of the airways by smoking leads to

• A. improved filtering of dust
• B. faster removal of mucus
• C. accumulation of mucus and debris, producing the smoker's cough
• D. widening of the trachea

Explanation: Healthy cilia sweep mucus and trapped particles upwards, and when smoke paralyses them the debris collects instead. The cough is the body's substitute for the lost escalator.

32. Giving up smoking is particularly difficult mainly because

• A. tobacco is inexpensive
• B. cigarettes contain essential vitamins
• C. withdrawal produces no symptoms
• D. nicotine produces strong physical and psychological dependence

Explanation: Nicotine reaches the brain within seconds and alters reward pathways, so stopping brings cravings and withdrawal. Dependence, not price, is why most smokers need repeated attempts to quit.

33. The risk of lung cancer in a smoker rises with

• A. the brand of cigarette
• B. the time of day the cigarettes are smoked
• C. the length of the filter
• D. the number of cigarettes per day and the number of years of smoking

Explanation: Cancer risk follows cumulative dose: each cigarette adds exposure to carcinogens over years of tissue damage. No brand or filter makes the dose safe.

34. Smoking destroys the walls of the alveoli irreversibly, permanently reducing the respiratory surface. This disease is called

• A. emphysema
• B. asthma
• C. pneumonia
• D. bronchitis

Explanation: The merged, ragged air spaces of emphysema cannot transfer enough oxygen, leaving the patient breathless even at rest. Unlike bronchitis, the structural damage cannot be undone by drugs.

35. Which statement about hookah or shisha smoking is correct?

• A. It is safer than cigarettes because the smoke passes through water
• B. It also delivers nicotine, tar and carbon monoxide and is harmful
• C. It contains no tobacco at all
• D. It affects only the mouth

Explanation: The water cools the smoke but removes little tar or CO, and sessions are long, so intake is substantial. The belief that the water filters out harm is the myth this question tests.

36. The most effective way to reduce smoking related disease in a population is

• A. treating lung cancer at an earlier stage
• B. giving antibiotics to all smokers
• C. preventing people from starting and supporting smokers to quit
• D. switching smokers to cigars

Explanation: Emphysema and cancer are largely irreversible once established, so prevention and cessation save far more lives than treatment of late disease. Cigars carry the same tobacco harms.

37. Tidal volume is approximately

• A. 500 mL
• B. 3000 mL
• C. 1200 mL
• D. 6000 mL

Explanation: Tidal volume (air in normal breath) is about 500 mL at rest in healthy adults.

38. The respiratory center is located in the

• A. Cerebrum
• B. Cerebellum
• C. Medulla oblongata
• D. Hypothalamus

Explanation: The respiratory center in the medulla oblongata controls breathing rate and depth.

39. The primary function of larynx is:

• A. Humidifying air
• B. Filtering dust
• C. Gaseous exchange
• D. Voice production

Explanation: The larynx houses the vocal cords, and air forced between them makes them vibrate to produce sound, which is why it is called the voice box. Humidifying and filtering the air are done earlier, in the nasal cavity and the ciliated mucous lining of the airways. Gaseous exchange happens only in the alveoli, since no other part of the tract has walls thin enough.