And space number seven is the alveolar sac space. And this entire orange section is our alveolar sack. That is described by number six. Now if we notice along our bronchio we also have these regions shown by red. So this portion, this portion, this portion, and that is our smooth muscle that extends around our bronchiol and it is capable of contracting and dilating that bronchiole as needed. Now notice we have many of these individual tiny balloon like structures shown by number one and those are our alveoli.