Ventilation

Flussdiagrammknoten

• Inspiration

• The external inter costal and diaphragm muscles contract.

• This causes the rib cage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thoracic cavity.

• As the volume of the thoracic cavity increases, the lung pressure decreases.

• Air will always flow from an area of high pressure to an area of lower pressure so air flows down the trachea and into the lungs.

• Inspiration is an active process-it requires energy.

• Expiration

• The external inter costal and diaphragm muscles relax.

• The internal inter costal muscles contract pulling the rib cage further down and in. During this time the movement of two sets of intercostal muscles are said to be antagonastic.

• The volume of the thoracic cavity decreases, causing the air pressure to increase.

• Air is forced down the pressure gradient and out of the lungs.

• Normal expiration is a passive process - it doesn't require energy.