Oblique Head of the Abductor Pollicis Under the Skin, Palmar View

Description

Presented from a palmar (volar) perspective beneath intact skin, the thenar compartment is centered on the thumb ray with the first metacarpal lying lateral to the second and the proximal and distal phalanges of the thumb aligned distal to the metacarpophalangeal joint. Superficial thenar fibers consistent with abductor pollicis brevis and opponens pollicis sit radial and anterior to the carpus, while the deeper adductor pollicis oblique head can be inferred coursing from the capitate and bases of the second and third metacarpals toward the ulnar side of the base of the proximal phalanx of the thumb. Carpal anatomy is clearly organized proximally to distally, with the trapezium at the radial distal row supporting the first carpometacarpal joint. Joint cartilage is emphasized at the MCP and CMC articulations. Strong landmarks. Palmar anatomy of the thenar muscles matters because thumb opposition and precision pinch depend on coordinated action across the trapeziometacarpal joint, not just the thumb phalanges. Median nerve dysfunction at the carpal tunnel commonly presents as weakness of abductor pollicis brevis and opponens pollicis with thenar flattening, while ulnar nerve lesions can spare those muscles yet compromise power pinch through adductor pollicis (including the oblique head), a distinction that guides bedside motor testing and electrodiagnostic interpretation. This view also supports teaching the surgical corridor used in basal joint arthroplasty or trapeziectomy, where preserving thenar soft tissue planes helps maintain postoperative thumb stability. Hand anatomy courses and occupational therapy modules use this type of palmar dissection-style rendering to connect bony architecture of the carpus and metacarpals with functional muscle vectors at the thumb. It also fits orthopedic and plastic surgery publications discussing carpal tunnel release, thenar atrophy, and reconstruction of thumb opposition. Anatomical accuracy verified by SciePro's Medical Advisory Board.