Breathing & gas exchange

BREATHING IN

The diaphragm contracts and moves down.

Chest space increases. Air pressure falls. Air flows in.

BREATHING OUT

The diaphragm relaxes and moves up.

Chest space decreases. Air pressure rises. Air flows out.

AT THE ALVEOLI

Oxygen moves from the air into the blood.

Carbon dioxide moves from the blood into the air.

Breathing moves air. Respiration releases energy inside cells.