That is where gas exchange actually takes place. So essentially this space, number seven, the alveolar sax space, connects directly to the space within each one of these alveoli and that is known as the alveolar space. So if we examine each one of these alveoli, we basically get the following diagram. And the space inside each one of these tiny alveoli looks something like this. That's the alveolar space. It's not the same as the alveolar sack space, but they are connected to one another.