What type of muscle is present in the air passages?

Smooth muscle is the type of muscle that is present in the air passages, including the bronchial tubes and bronchioles of the respiratory system. This type of muscle is involuntary, meaning it operates without conscious control, which is essential for the automatic regulation of airflow and bronchoconstriction or bronchodilation in response to various stimuli, such as allergens or irritants.

Smooth muscle cells are characterized by their spindle shape and lack of striations, which distinguishes them from skeletal and cardiac muscles. In the air passages, smooth muscle plays a crucial role in regulating the diameter of the airways, enabling the body to control airflow to the lungs based on its needs, such as during exercise or at rest. This adaptability is vital for maintaining effective respiration in varying conditions.