Which statement about the defense mechanisms of the pediatric respiratory tract is correct?
Alveolar macrophages are part of the adaptive immune system and provide specific antibody responses.
Lymphoid tissue like tonsils and adenoids provide local immune surveillance and defense.
The cough and sneeze reflexes in infants are stronger and more effective than in adults.
Secretory Immunoglobulin A (sIgA) in mucosal secretions provides a form of passive immunity.
The Correct Answer is B
Lymphoid tissues such as the tonsils and adenoids form part of the Waldeyer’s ring and play a vital role in local immune surveillance of the upper respiratory tract, detecting and responding to inhaled or ingested pathogens.
Rationale for correct answer:
2. Lymphoid tissue like tonsils and adenoids provide local immune surveillance and defense. These structures contain immune cells (B and T lymphocytes) that detect antigens entering through the nose and mouth, initiating immune responses to help prevent infection spread.
Rationale for incorrect answers:
1. Alveolar macrophages are part of the innate immune system, not adaptive immunity. They engulf and destroy pathogens and debris but do not produce specific antibodies.
3. Infants’ cough and sneeze reflexes are actually less forceful and less coordinated than adults’, making clearance of secretions less efficient.
4. Secretory Immunoglobulin A (sIgA) is part of the active mucosal immune system, not passive immunity. Passive immunity is typically acquired via maternal antibodies (e.g., IgG via placenta, IgA via breast milk).
Take home points
- The pediatric respiratory tract uses multiple defense layers: mechanical (mucociliary clearance), reflexive (cough/sneeze), and immune (lymphoid tissue, sIgA, macrophages).
- Tonsils and adenoids are particularly important in early childhood but can also be a site of chronic infection or hypertrophy leading to obstruction.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Infants and young children have anatomical and physiological differences in their upper airways compared to adults that increase their risk for airway obstruction. These differences include a smaller and more flexible airway structure and narrower passages, which make them more vulnerable to swelling and obstruction.
Rationale for correct answer:
1. Underdeveloped cricoid cartilage and narrow nasal passages contribute significantly to the increased risk of upper airway obstruction in infants and children. The cricoid cartilage is the narrowest part of a child’s airway and is less rigid than in adults, making it more prone to collapse or swelling. Narrow nasal passages can become easily blocked by secretions or inflammation, further compromising airflow.
Rationale for incorrect answers:
2. Tonsils in children tend to be relatively large, not small, and can contribute to obstruction. The nasal passages are narrow, but this option misses the critical role of cricoid cartilage development.
3. The child’s larynx is funnel-shaped, not cylindrical, with the narrowest point at the cricoid cartilage. While sinuses develop over time, their underdevelopment doesn’t directly increase risk of upper airway obstruction.
4. Children actually have proportionally larger tongues relative to their oral cavity, which can contribute to obstruction, so “smaller tongue” is inaccurate.
Take home points
- Infants and children have a funnel-shaped, narrower airway with a less rigid cricoid cartilage, making them more susceptible to airway obstruction.
- Narrow nasal passages add to the risk by limiting airflow, especially during inflammation.
- Understanding these anatomical differences is critical when assessing respiratory distress in pediatric patients.
Correct Answer is D
Explanation
The primary reason a small degree of inflammation in a child’s airway causes a disproportionately large increase in airway resistance is the significantly narrower airway diameter. According to Poiseuille’s law, resistance to airflow is inversely proportional to the fourth power of the radius, meaning even a slight reduction in airway size greatly increases resistance.
Rationale for correct answer:
4. A child’s airway is much narrower than an adult’s, so swelling or mucus buildup reduces the radius substantially, causing a dramatic increase in resistance and work of breathing. This makes conditions like croup or bronchiolitis more severe in young children.
Rationale for incorrect answers:
1. While children do have higher metabolic rates and oxygen demands, this is not the main reason for the exaggerated effect of inflammation on airway resistance.
2. The cartilaginous and flexible trachea in infants contributes to collapsibility but does not explain the disproportionate rise in resistance from swelling.
3. Greater diaphragmatic reliance affects breathing mechanics but not the mathematical relationship between airway narrowing and resistance.
Take home points
- Airway resistance is highly sensitive to changes in radius, especially in children due to their small baseline diameters.
- Even minor airway swelling (e.g., 1 mm circumferential edema) can reduce the cross-sectional area by more than half in a child.
- Rapid recognition and management of pediatric airway inflammation is critical to prevent respiratory distress and hypoxia.
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