Living Environment Regents Practice Test 2025 – Complete Exam Prep

The primary function of the alveolus in the human lung is to facilitate gas exchange. Alveoli are tiny air sacs located at the end of the respiratory bronchioles, and they play a crucial role in the respiratory system. Their structure provides a large surface area and a thin barrier, making them highly efficient for gas exchange between the air in the lungs and the blood in the capillaries surrounding them.

When we inhale, oxygen from the air fills the alveoli. The oxygen then diffuses across the alveolar membrane into the bloodstream, where it binds to hemoglobin in red blood cells to be transported to tissues throughout the body. At the same time, carbon dioxide, which is a waste product of cellular respiration, moves from the blood into the alveoli to be exhaled out of the body. This process is vital for maintaining proper oxygen levels in the blood and removing carbon dioxide, thus playing a critical role in respiration and overall metabolic function.

The other options incorrectly attribute functions to the alveoli that are managed by different systems in the body. For instance, absorbing nutrients is primarily the job of the digestive system, while hormone production is typically associated with endocrine glands. Storing energy relates more to fat cells and other storage mechanisms in