The Respiratory System

External Intercostal Muscles- muscles of inspiration that move the rib cage upwards & outwards during inspiration. Internal Intercostal Muscles- muscles used for expiration during exercise.Sterno-cleidomastoid-  (muscle from ear joining at base of throat) is accessory muscle that aids inspiration when breathing rate & depth increases.  Scalenes- 3 neck muscles, are accessory muscles that also aid inspiration when breathing rat & depth increases.

Inspiration- EIM contracts, diaphragm contracts downwards (flattens), ribcage moves upwards & outwards, volume of thoracic cavity increases, pressure of air within lungs falls, air is drawn into lungs

Expiration- EIM relax, diaphragm relaxes (dome shaped), ribcage moves downwards & inwards, volume of thoracic cavity decreases, pressure of air in lungs increases, air is forced out of the lungs.