Internal Intercostals - Podcast Version TeachMeAnatomy 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 (2025) 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 Rate This Article