Posterior Perspective of the External Intercostal Muscles Beneath the Skin

Description

Seen from the back with the skin removed, the paired external intercostal muscles fill the intercostal spaces along the posterolateral thoracic wall, spanning from the inferior border of each rib to the superior border of the rib below. Their fibers run obliquely infero-anteriorly (the classic “hands-in-pockets” direction), appearing thickest near the rib angles where they lie lateral to the thoracic spinous processes and medial to the scapular margins. Posterior elements of the vertebral column anchor the scene at the midline, while the ribs sweep laterally beneath the scapulae toward the axilla. Bone landmarks are clear. External intercostals are the primary intercostal elevators during inspiration, and the posterior view emphasizes the segment where their muscular portion is most robust before transitioning anteriorly into the external intercostal membrane near the costochondral junction. That distinction matters when teaching thoracic wall mechanics and when planning posterolateral thoracotomy or chest tube placement, where layered dissection crosses serratus anterior, the intercostal spaces, and the neurovascular bundle sheltered along the inferior rib margin. Rib fractures near the angle can disrupt these fibers and contribute to painful splinting, limiting rib cage expansion. Use this artwork for gross anatomy and respiratory physiology modules, for surgical anatomy figures in thoracic or trauma publications, or as patient-facing educational content explaining why posterior rib injuries hurt during breathing and coughing. Clean posterior orientation makes it easy to pair with diagrams of intercostal nerve blocks and safe needle placement relative to the rib. Anatomical accuracy verified by SciePro's Medical Advisory Board.