They Are What Make up the Lungs

The alveoli (singular: alveolus) are small air sacs that look like balloons, and they make up the lungs.  Therefore, when air enters into the lungs, each alveolus is inflated with air like tiny little balloons.

small air sacs…like balloons

20170506 Alveoli
(Click to Enlarge)

Because each alveolus is covered with capillaries, blood  can exchange oxygen with carbon dioxide with the air inside an alveolus.  Therefore, blood takes oxygen from the air inside an alveolus while dumping carbon dioxide into that air.  After this exchange is done, the air can be pushed out of the lungs in an “exhale” movement.


Next Generation Science Standards:

MS-LS1-3 Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells.

HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

HS-LS1-3 Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

What Science Does this Comic Teach?

Unit: Anatomy

⇒Chapter: Respiratory System

⇒Topic: alveoli

Additional Information


They are tiny little blood vessels spread all over the body.  For more information, see this comic:

Oxygen (O2)

Most organisms need oxygen to survive–including humans.  Without oxygen, our tissues will die in a matter of minutes.  We breathe in oxygen.

Carbon Dioxide (CO2)

To animals, carbon dioxide is a waste, and it must be removed from the body.  However, plants use this gas to conduct photosynthesis.

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