Final answer:
Surface tension in the lungs increases when there's insufficient pulmonary surfactant produced by type II alveolar cells. Without surfactant, the alveoli may collapse, resulting in increased resistance to airflow and difficulty in breathing.
Step-by-step explanation:
Increase in surface tension occurs if alveolar type II cells are not producing sufficient pulmonary surfactant. This may result in the collapse of alveoli and an increase in resistance to air flow.
Type II alveolar cells are crucial for producing pulmonary surfactant which maintains the stability of the alveoli by reducing surface tension. In the absence of sufficient surfactant, alveoli are at risk of collapsing, particularly during expiration, leading to increased work of breathing and potential respiratory distress.
This condition can significantly reduce the lungs' compliance, making breathing laborious. The increased resistance to airflow seen when the alveoli collapse is explained by the air needing to move through narrowed airways, which increases the effort required to ventilate the lungs.