What are the smaller subdivisions of bronchi in the lungs called?

The smaller subdivisions of bronchi in the lungs are known as bronchioles. These structures branch from the larger bronchi, progressively getting smaller and leading deeper into the lungs. Bronchioles play a crucial role in the respiratory system as they are the passages through which air flows to the alveoli, where gas exchange occurs.

Bronchioles lack cartilage in their walls, which distinguishes them from the primary and secondary bronchi that contain cartilage to keep the airways open. Additionally, bronchioles are lined with smooth muscle, allowing for regulation of airflow through bronchoconstriction and bronchodilation, crucial for maintaining adequate ventilation during different physiological demands.

In contrast, alveoli refer to the tiny air sacs at the end of the bronchioles where oxygen and carbon dioxide are exchanged. Capillaries are tiny blood vessels that surround the alveoli, facilitating the exchange of gases but are not themselves subdivisions of the bronchi. The pleura refers to the double-layered membrane surrounding the lungs, providing a protective barrier and allowing for smooth movement during breathing, but it does not have a direct role in the subdivision of bronchi.