Questions & explanations
1. Which of the following best describes the primary cause of breathing difficulty in asthma?
- Inflammation of the bronchi and bronchioles
- Damage to the alveolar walls
- Excessive mucus production in the trachea
- Paralysis of the diaphragm
Answer: Inflammation of the bronchi and bronchioles
Asthma involves inflammation of the bronchi and bronchioles, leading to wheezing and difficulty in breathing. Damage to alveolar walls is characteristic of emphysema, not asthma. Excessive mucus production can occur but is not the primary cause; paralysis of the diaphragm is unrelated.
2. Occupational respiratory disorders are common in industries involving:
- Grinding or stone-breaking
- Food processing
- Textile weaving
- Electronics assembly
Answer: Grinding or stone-breaking
Industries with grinding or stone-breaking produce large amounts of dust that can overwhelm lung defenses, leading to occupational respiratory disorders. Food processing, textile weaving, and electronics assembly generally do not produce such hazardous dust levels.
3. In asthma, the narrowing of airways is primarily due to:
- Spasm of smooth muscles in the walls of bronchi and bronchioles
- Accumulation of fluid in the alveoli
- Thickening of the pleural membranes
- Collapse of the trachea
Answer: Spasm of smooth muscles in the walls of bronchi and bronchioles
In asthma, bronchoconstriction occurs due to spasm of smooth muscles in the bronchial walls, narrowing the airways. Fluid accumulation in alveoli is seen in pulmonary edema; pleural thickening is not a feature of asthma; tracheal collapse is a different condition.
4. Which of the following receptors can detect changes in CO2 and H+ concentration and send signals to the respiratory rhythm centre?
- A. Chemoreceptors in the medulla oblongata
- B. Carotid and aortic bodies
- C. Stretch receptors in the lungs
- D. Irritant receptors in the airways
Answer: B. Carotid and aortic bodies
The carotid and aortic bodies, located near the carotid artery and aortic arch respectively, are peripheral chemoreceptors that sense changes in CO2 and H+ concentration. They send signals to the respiratory rhythm centre to adjust breathing accordingly.
5. A chemosensitive area located near the respiratory rhythm centre is highly sensitive to which of the following?
- A. Increase in O2 concentration
- B. Decrease in CO2 concentration
- C. Increase in CO2 and H+ concentration
- D. Decrease in H+ concentration
Answer: C. Increase in CO2 and H+ concentration
The chemosensitive area adjacent to the rhythm centre is highly sensitive to changes in CO2 and H+ levels. An increase in these substances activates the centre, which then signals the rhythm centre to increase ventilation to eliminate excess CO2 and H+.
6. The anatomical setup of the lungs in the thorax ensures that any change in the volume of the thoracic cavity is reflected in the lung cavity. This is because:
- A. The lungs are directly attached to the thoracic wall.
- B. The pleural membranes are continuous and the pleural cavity is a closed space with negative pressure.
- C. The diaphragm is the only muscle involved in breathing.
- D. The lungs are filled with air and expand passively.
Answer: B. The pleural membranes are continuous and the pleural cavity is a closed space with negative pressure.
The pleural membranes (visceral and parietal pleura) are continuous and enclose a closed pleural cavity with negative pressure. This negative pressure couples the lungs to the thoracic wall, so any change in thoracic volume is transmitted to the lungs.
7. Emphysema is characterized by:
- Damage to alveolar walls reducing the respiratory surface area
- Inflammation of the bronchi and bronchioles
- Excessive mucus secretion in the airways
- Spasm of the diaphragm
Answer: Damage to alveolar walls reducing the respiratory surface area
Emphysema involves destruction of alveolar walls, decreasing the surface area for gas exchange. Inflammation of bronchi is typical of asthma; excessive mucus is seen in chronic bronchitis; diaphragmatic spasm is not a feature of emphysema.
8. What is the approximate volume of air that remains in the lungs even after a forcible expiration?
- 500 mL
- 1100-1200 mL
- 2500 mL
- 3500 mL
Answer: 1100-1200 mL
Residual volume (RV) is the air left in the lungs after a maximal forced expiration, averaging 1100-1200 mL. 500 mL is typical tidal volume, 2500 mL is approximate inspiratory reserve volume, and 3500 mL is near vital capacity in adults.
9. Shortness of breath in emphysema results from:
- Reduced gaseous exchange due to damaged alveolar walls
- Narrowing of the trachea due to inflammation
- Increased mucus production in the bronchi
- Spasm of the bronchiolar smooth muscles
Answer: Reduced gaseous exchange due to damaged alveolar walls
In emphysema, alveolar wall damage reduces the surface area for gas exchange, leading to shortness of breath. Tracheal narrowing is not typical; increased mucus is seen in bronchitis; bronchiolar spasm is characteristic of asthma.
10. Which of the following correctly describes the two stages of breathing?
- Inspiration draws atmospheric air in; expiration releases alveolar air out.
- Inspiration releases alveolar air out; expiration draws atmospheric air in.
- Both inspiration and expiration involve active muscle contraction.
- Inspiration and expiration are passive processes.
Answer: Inspiration draws atmospheric air in; expiration releases alveolar air out.
Breathing consists of inspiration (inhalation) where atmospheric air enters the lungs, and expiration (exhalation) where alveolar air is expelled. The other options reverse the processes or incorrectly describe muscle activity.
11. Which of the following statements is true regarding the role of oxygen in the regulation of respiratory rhythm?
- A. Oxygen is the primary stimulus for breathing under normal conditions
- B. A decrease in oxygen levels strongly stimulates the respiratory centre
- C. The role of oxygen in regulating respiratory rhythm is quite insignificant
- D. Oxygen directly acts on the chemosensitive area to increase ventilation
Answer: C. The role of oxygen in regulating respiratory rhythm is quite insignificant
Under normal conditions, the respiratory rhythm is primarily regulated by CO2 and H+ levels, not oxygen. Oxygen levels only become significant in extreme hypoxia, but generally, its role in day-to-day regulation is minimal.
12. Which of the following structures in the respiratory tract is NOT supported by incomplete cartilaginous rings?
- A. Trachea
- B. Primary bronchus
- C. Secondary bronchus
- D. Alveoli
Answer: D. Alveoli
The trachea, primary, secondary, and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings, but alveoli are thin-walled, vascularised bag-like structures without cartilaginous support.