What physiological change decreases resistance by opening the airways?

• A. Increased airway diameter
• B. Increased lung volume
• C. Decreased airway pressure
• D. Decreased lung compliance

Answer: (B)

The correct answer is related to the concept of airway resistance and how the mechanics of ventilation can affect airflow through the respiratory system. When there is an increase in lung volume, particularly during inspiration, the expansion of the thoracic cavity generates negative pressure within the lungs. This negative pressure causes the airways, including the bronchi and bronchioles, to expand.

As the airways open up and their diameter increases due to this expansion, resistance to airflow decreases significantly. This allows for greater air exchange and more efficient ventilation. The physiological principle at work here is that increased lung volume promotes the widening of the airway passages, thus facilitating easier passage of air.

The focus on increased airway diameter directly ties to how the muscles surrounding the airways, particularly the bronchial smooth muscles, respond to the changes in lung volume. When lung volume increases, the surrounding structures help keep the airways open, reducing resistance.

Other options, while they might be related concepts in the broader context of respiratory physiology, do not directly answer the question as precisely as increased lung volume does. Increased airway diameter and decreased airway pressure are both results of increased lung volume rather than the primary mechanism causing decreased resistance. Decreased lung compliance typically indicates stiffer lungs, which would likely lead to increased