What respiratory structure regulates lung ventilation by constricting and dilating?

The bronchioles are responsible for regulating lung ventilation by constricting and dilating. They are the smallest branches of the bronchial tree, the system of airways that conduct air to and from the lungs during respiration. The diameter of the bronchioles is controlled by the autonomic nervous system, which regulates involuntary functions such as heart rate, digestion, and breathing. When the body needs to increase airflow to the lungs, the bronchioles dilate, allowing more air to pass through. Conversely, when the body needs to decrease airflow, the bronchioles constrict, limiting the amount of air that can enter or leave the lungs. This regulation of bronchiole diameter is essential for maintaining proper lung ventilation and gas exchange.