What does the alveoli of the lungs of a mammal do?

The alveoli are tiny air sacs in the lungs of mammals that are crucial for gas exchange. They provide a large surface area for oxygen to diffuse into the bloodstream and for carbon dioxide to be expelled from the blood. The thin walls of the alveoli, along with their extensive capillary networks, facilitate this efficient exchange, allowing mammals to breathe and sustain cellular respiration.