The primary function of the mucociliary clearance system is to:
Remove foreign particles and pathogens from the airways by trapping and sweeping them out.
Facilitate gas exchange by keeping the alveolar surface moist.
Provide systemic adaptive immunity against bacterial infections.
Regulate blood pressure through the production of angiotensin-converting enzyme (ACE).
The Correct Answer is A
The mucociliary clearance system is a key innate defense mechanism of the respiratory tract, designed to trap and remove inhaled particles, pathogens, and debris before they reach the lower airways and alveoli.
Rationale for correct answer:
1. The respiratory epithelium contains mucus-producing goblet cells and ciliated cells. Mucus traps inhaled contaminants, and coordinated ciliary beating moves the mucus upward toward the pharynx, where it can be swallowed or expectorated. This process helps prevent infections and maintains airway cleanliness.
Rationale for incorrect answers:
2. While moisture in the alveoli facilitates gas exchange, this is not the main role of the mucociliary clearance system, alveolar moisture regulation is handled by surfactant and fluid balance mechanisms, not cilia and mucus.
3. Adaptive immunity involves lymphocytes and antigen-specific responses, which are separate from the mechanical clearance provided by the mucociliary system.
4. Angiotensin-converting enzyme (ACE) production occurs mainly in the pulmonary capillary endothelium, not as part of mucociliary clearance.
Take home points
- The mucociliary escalator is an essential first-line defense in the respiratory tract.
- Smoking, dehydration, and certain diseases (e.g., cystic fibrosis, primary ciliary dyskinesia) can impair this system, increasing infection risk.
- Efficient mucociliary function is especially important in children, whose immune systems are still developing.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
The diaphragm is the primary muscle of respiration in newborn infants. This is significant because their intercostal muscles are underdeveloped, and their rib cages are highly compliant, so they rely almost entirely on diaphragmatic movement for ventilation.
Rationale for correct answer:
3. In newborns, diaphragmatic contraction creates negative pressure to draw air into the lungs. If the diaphragm tires due to illness, hypoxia, or increased work of breathing, ventilation can rapidly deteriorate since accessory muscle use is limited.
Rationale for incorrect answers:
1. Sternocleidomastoid muscles are accessory muscles used during respiratory distress, not for quiet breathing in healthy infants.
2. Intercostal muscles are not fully developed in newborns and provide minimal contribution to chest wall stability or ventilation.
4. Abdominal muscles assist in forced exhalation and coughing but are not the primary drivers of quiet respiration.
Take home points
- Infants’ dependence on the diaphragm makes them vulnerable to respiratory fatigue in prolonged distress.
- Conditions that impair diaphragmatic function (e.g., sepsis, neuromuscular disorders, fatigue from tachypnea) can cause rapid deterioration.
- Early recognition of increased work of breathing is essential, as infants have limited reserves.
Correct Answer is D
Explanation
Retractions are a clinical sign of increased work of breathing, often seen in infants and children. They occur when soft tissues around the chest wall are pulled inward during inspiration due to negative intrathoracic pressure, usually because the child is struggling to get enough air into the lungs.
Rationale for correct answer:
4. D: Substernal retractions are inward pulling of the soft tissue just beneath the sternum/xiphoid (subxiphoid/epigastric area). This reflects increased negative intrathoracic pressure and is common in moderate- severe respiratory distress.
Rationale for incorrect answers:
1. A: This represents suprasternal retractions, typically seen at the sternal notch with upper-airway obstruction (e.g., croup, laryngomalacia). Not “substernal.”
2. B: The xiphoid itself is the bony tip; retractions are named for the soft tissue below it (subxiphoid/substernal). At the xiphisternum isn’t the same as below the sternum.
3. C: Those are intercostal retractions along the lateral chest wall, not beneath the sternum.
Take home points
- Retractions are classified by location: suprasternal (above sternum), intercostal (between ribs), subcostal (below ribs), and substernal (below sternum).
- The more severe the respiratory distress, the more locations you may see retractions in simultaneously.
- Substernal retractions often point to lower airway or lung pathology (e.g., bronchiolitis, asthma, pneumonia).
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