Category: and the internal intercostal muscle contract. The diaphragm muscle relaxes and assumes its normal dome shape. The ribcage moves downwards and inwards. Volume in the thoracic cavity reduces
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causing them to expand. Air flows to the alveoli where gaseous exchange takes place.
Expiration
Expiration is the net movement of air out of the lungs. This process is defined to be passive because it doesnt require energy. The external intercostal muscles relax
decreasing the pressure. The pressure difference between the external environment and the lungs causes air to move into the lungs