Definition:Breathing (or ventilation) is the process of taking air into the lungs (inhalation) and pushing air out of the lungs (exhalation).

Two stages of breathing

1. Inhalation (Breathing in)

• The diaphragm contracts and moves downward.

• The rib muscles contract, moving the ribs up and out.

• The chest cavity gets bigger.

• Pressure inside the lungs decreases.

• Air moves into the lungs.

2. Exhalation (Breathing out)

• The diaphragm relaxes and moves upward.

• The rib muscles relax, moving the ribs down and in.

• The chest cavity gets smaller.

• Pressure inside the lungs increases.

• Air moves out of the lungs.

Why is breathing important?

• Brings oxygen into the body.

• Removes carbon dioxide from the body.

• Helps cells carry out cellular respiration to release energy.