Bronchioles are small, thin-walled airways in the lungs that branch off from the bronchi, which are the larger air passages. They play a crucial role in conducting air to the alveoli, where gas exchange occurs. Bronchioles also help regulate airflow and can constrict or dilate in response to various stimuli, influencing airflow resistance and overall lung function. Additionally, they are lined with smooth muscle and mucus-secreting cells, which help trap particles and protect the respiratory system.