Transcript

During inhalation, the diaphragm contracts, causing it to flatten out and move downwards. At the same time, the ribs are moved upwards and outwards by contraction of the external intercostal muscles. Contraction of the diaphragm and the external intercostal muscles increases the volume within the ribcage so that there is a larger area for the lungs to expand into. This creates a pressure gradient within the thoracic cavity that draws air into the lungs.