Internal Intercostals - Podcast Version 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x The internal intercostals are a muscle of the thoracic wall. They lie deep to the external intercostal muscles. Their fibres are orientated in an inferior and posterior direction. Attachments: Originates from the lateral edge of the costal groove and inserts onto the superior surface of the rib below. Actions: Stablises the position of the ribs during normal respiration. Depresses the ribs and decreases the thoracic volume during forced expiration. Innervation: Intercostal nerves (T1-T11). Blood supply: Anterior and posterior intercostal arteries By TeachMeSeries Ltd (2026) Fig 1The external and internal intercostals of the thoracic wall. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Pro Feature - Dissection Atlas Prosection of the muscles of the thoracic wall. Prosection of the muscles of the thoracic wall. You've Discovered a Pro Feature Access our Dissection Image Library Enhance your understanding with high-resolution dissection images showcasing real-life anatomy. Learn More Frequent questions What are the internal intercostals? The internal intercostals are muscles located in the thoracic wall, positioned beneath the external intercostal muscles. They play a key role in stabilising the ribs and facilitating respiration. What is the function of the internal intercostals? The primary function of the internal intercostals is to stabilise the ribs during normal breathing. Additionally, they depress the ribs to reduce thoracic volume during forced expiration. Where do the internal intercostals attach? The internal intercostals originate from the lateral edge of the costal groove and insert onto the superior surface of the rib beneath. This anatomical positioning is crucial for their function during respiration. What nerves innervate the internal intercostals? The internal intercostals are innervated by the intercostal nerves, which range from T1 to T11. This nerve supply is essential for muscle contraction and respiratory mechanics. How are the internal intercostals supplied with blood? The blood supply to the internal intercostals comes from both the anterior and posterior intercostal arteries. This vascularisation ensures the muscles receive the necessary nutrients and oxygen for their function. Rate This Article