Science of Conflict

Alveoli.

As the trachea moves into the lung tissue it divides into smaller and smaller tubes that finally end up in small sac like structures called alveoli. These look like bunches of grapes from the outside and are well supplied with tiny blood vessels called capillaries. Gas exchange occurs in the alveoli where oxygen is taken into the blood and carbon dioxide released to the atmosphere. The structure of the alveoli increases the area where gas exchange can take place. If all the alveoli in the lungs were to be cut open and placed on the ground they would occupy an area the size of a tennis court.