Mechanics of expiration

During expiration muscles of ribs are relaxed and ribs move downward and

inward.

You know what relaxed mean

Chest cavity becoming small in size

• When ribs are relaxed, space of chest gets less.

What happens to diaphragm

• Muscles of diaphragm also relax and they become more domelike in shape, so chest cavity is also reduced from floor.

Check the width of chest cavity

• This reduction in space of chest cavity exert pressure on lungs.

Air moves out of lung

• When the lungs are pressed ,the air moves out of lungs and this process is called expiration.