External Intercostals - Podcast Version 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x The external intercostals are a muscle of the thoracic wall. They are the most superficial of the intercostal muscles. Their fibres are orientated in an inferior and anterior direction. Attachments: Originates at the lower border of each rib, inserting onto the superior border of the rib below. Actions: Elevates the ribs and increases the thoracic volume during inspiration. 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 external intercostals? The external intercostals are muscles located in the thoracic wall, specifically the most superficial layer among the intercostal muscles. They play a crucial role in the mechanics of breathing. What is the function of the external intercostals? The primary function of the external intercostals is to elevate the ribs, which increases the volume of the thoracic cavity during inhalation. This action is essential for effective respiration. Where do the external intercostals attach? The external intercostals originate from the lower border of each rib and insert onto the superior border of the rib directly below. This arrangement facilitates their role in rib elevation. How are the external intercostals innervated? The external intercostals are innervated by the intercostal nerves, specifically from T1 to T11. This nerve supply is vital for their contraction during breathing. What is the blood supply to the external intercostals? The blood supply for the external intercostals comes from the anterior and posterior intercostal arteries. These vessels ensure the muscles receive the necessary nutrients and oxygen for their function. Rate This Article