How Air Enters And Leaves The Thorax

Air always moves from a high to a low pressure. So in order
for air to enter our lungs, a low pressure ust be created.
The intercostal muscles between the ribs contract and our
ribs move up and out. The diaphragm contracts and moves
down. Now the voulume has been increased and the pressure
decreased.

Air now automatically enters the thorax via the trachea,
right and left bronchus and bronchioles until finally it reaches
the air sacs or alveoli. Here gas exchange accurs.

Now air rich in carbon dioxide and water vapour has to leave
the thorax. The pressure has to increase. This is done by
decreasing the volume. The muscles between the ribs relaxe,
and the ribs move down and in. The diaphragm relaxes and
moves up. Air pressure is higher inside than outside so the air
automatically leaves the thorax.

© Miss. Scroggie & Eva de Schipper, B2a

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