What these tiny sacs in the lungs do and conditions that can affect them Medically reviewed by Susan Russell, MD Alveoli are ...

When air goes down into the lungs, it passes through smaller and smaller tubes and ends up in tiny air sacs called alveoli. Oxygen passes through the walls of the alveoli and enters tiny blood ...

Gas exchange is a process that involves the swapping of gases that occurs at exchange surfaces such as the alveoli found within your lungs. Gas exchange allows oxygen to travel into your cells for ...