2.47: Understand the Role of the Intercostal Muscles and the Diaphragm in Ventilation

INHALATION	EXHALATION
Diagram showing Organs during Inhalation	Diagram showing Organs during Exhalation
External intercostal muscles contract, pulling rib cage upwards and outwards Internal intercostal muscles relax and are pulled back to their elongated state Diaphragm contracts and flattens, pushing abdomen walls outwards As a result, thoracic volume increases, causing pressure to decrease Decrease in pressure causes air to be drawn into lungs - inhalation	External intercostal muscles relax and are pulled back to their elongated state Internal intercostal muscles contract, pulling rib cage downwards and inwards Diaphragm relaxes and forms dome shape As a result, thoracic volume decreases, causing pressure to increase Increase in pressure causes air to be forced out of lungs - exhalation