Final answer:
Bronchioles are tiny airways without cartilage, encircled by smooth muscle and elastic fibers, that lead to alveoli where gas exchange occurs. They contain cilia and mucus to trap particulates and neuroendocrine cells for additional regulatory functions.
Step-by-step explanation:
Bronchioles Structure and Function
Bronchioles are small airways in the lungs that stem from the larger bronchi and continue to branch into progressively smaller tubes before ending in clusters of alveoli (air sacs). These bronchioles are encircled by smooth muscle and elastic fibers instead of cartilage, which allows for changes in diameter to regulate airflow. Their walls are lined with cilia and mucus-producing cells that trap and move particulates out of the lungs, protecting the respiratory system. Additionally, certain cells called neuroendocrine cells are among some of the cells lining the bronchioles, contributing to the regulation of airway constriction and local immunity.
The respiratory system's conducting zone includes the bronchioles which facilitate the passage of air to the alveoli, where gas exchange occurs. The bronchioles play a critical role in maintaining the patency of the airways during the respiratory cycle, and their smooth muscle is innervated by both parasympathetic and sympathetic nerves, which control constriction and dilation.
The presence of neuroendocrine cells within the bronchioles suggests a complex regulatory mechanism involved in respiratory function, extending beyond simple gas exchange. These specialized cells add another layer of control in response to varying conditions within the lungs, such as the presence of foreign particles or changes in air composition.