What is a key role of the diaphragm in respiration?

• A. Facilitating expiration
• B. Increasing lung volume during inhalation
• C. Regulating lung surfactant
• D. Preventing airway obstruction

Answer: (B)

The diaphragm plays a crucial role in respiration, particularly during inhalation, by increasing lung volume. When the diaphragm contracts, it moves downward toward the abdominal cavity, which creates a negative pressure in the thoracic cavity. This negative pressure allows air to flow into the lungs, thereby increasing lung volume as the air fills the expanding space. This mechanism is fundamental to the process of breathing, as it allows for effective gas exchange by ensuring that fresh oxygen enters the lungs.

In contrast, the other options do not accurately reflect the primary function of the diaphragm during respiration. While the diaphragm does aid in expiration, this occurs primarily when it relaxes rather than actively facilitates the process. Regulating lung surfactant is the role of alveolar type II cells and is not directly related to the diaphragm's function. Preventing airway obstruction involves other structural elements of the respiratory system rather than the diaphragm itself.