The flexor pollicis longus is a muscle within the deep compartment of the anterior forearm. Attachments: Originates from the anterior surface of the radius and surrounding interosseous membrane. The tendon passes through the carpal tunnel and attaches to the base of the distal phalanx of the thumb. Actions: Flexes the interphalangeal joint and metacarpophalangeal joint of the thumb. Innervation: Median nerve (anterior interosseous branch). Blood supply: Ulnar artery By TeachMeSeries Ltd (2025) Fig 1Deep flexor muscles of the anterior forearm. 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 Print Article Rate This Article