Transcript (en)

Alveolar type 2 cells produce surfactant. This is a substance that reduces surface tension within the alveoli, preventing them from collapsing and making it easier for them to expand during breathing. In the alveoli, oxygen from the air passes through the alveolar walls into the blood and the surrounding capillaries. At the same time, carbon dioxide from the blood passes into the alveoli to be exhaled.