What happens to the smooth muscle in the airways during inhalation?

During inhalation, the smooth muscle in the airways relaxes, which allows the bronchial passages to widen. This relaxation is critical as it reduces the resistance in the airways and facilitates the passage of air into the lungs. When the smooth muscle relaxes, the bronchi and bronchioles enlarge, providing a larger diameter for airflow. This process is essential for efficient ventilation and ensures that adequate oxygen levels are maintained in the body.

In contrast, contraction of the smooth muscle would narrow the airways, increasing resistance and making it more difficult for air to enter the lungs, which occurs in conditions like asthma. Tightening of the smooth muscle or leaving it unchanged would not contribute to efficient inhalation, making the relaxation of the smooth muscle a key aspect of proper respiratory mechanics during inhalation.