Intercostal muscles
Intercostal muscles undergo activation when we are breathing, as they act as a support mechanism. There are three types of intercostal muscle; External, Internal and innermost (11 pairs of each). During Inspiration, External muscles are used most, whereas during expiration Internal intercostal muscles are used more. These three muscles have the ability to move the ribs up as the are positioned between 'adjacent ribs' that line intercostal spaces[1].
The external intercostal muscles are activated during inhalation. During a deep breath in the external intercostal muscles contract to lift the ribcage up, increasing the volume of the thoracic cavity therefore decreasing the pressure. Due to the decreased pressure in the thoracic cavity air therefore, flows into the lungs.
Whereas, the internal intercostal muscles are used during exhalation. The internal intercostal muscles contract during exhalation to pull the ribcage inwards, decreasing the volume of the thoracic cavity and therefore increasing the pressure. Due to increased pressure, the air flows out from the lungs, allowing exhalation.
References
- ↑ Richard L.Drake, A.Wayne Vogl, Adam W.M Mitchell (2010). Gray's anatomy for students. 2nd edition. Philadelphia: Chuchill Livingstone. p149-151