What are the balloon-like air sacs in the lungs called?

The balloon-like air sacs in the lungs are called alveoli. These tiny structures are essential for the respiratory system as they are the primary sites where gas exchange occurs. Alveoli have thin walls that allow oxygen to pass from the air into the blood and carbon dioxide to move from the blood into the air to be exhaled. Their large surface area, due to their numerous and clustered arrangement, maximizes the efficiency of gas exchange, which is crucial for providing oxygen to the body and removing waste gases.

In contrast, bronchioles refer to the smaller branches that lead from the bronchi to the alveoli but are not involved in gas exchange themselves. Arteries are blood vessels that carry blood away from the heart, and atria are the chambers of the heart that receive blood. Neither of these options pertains to the lung's air sacs where essential respiratory processes occur. Understanding the specific role of alveoli in lung function is critical for comprehending respiratory physiology and health.