The distal tendons of what muscles form the "anatomical snuff box"?

• A. Abductor pollicis longus, Extensor pollicis longus, and Extensor pollicis brevis
• B. Abductor pollicis longus, Extensor pollicis longus, and Flexor pollicis longus
• C. Abductor pollicis brevis, Extensor pollicis longus, and Extensor pollicis brevis
• D. Flexor pollicis longus, Abductor pollicis longus, and Extensor pollicis longus

Answer: (A)

The anatomical snuff box is the triangular groove on the back of the hand at the base of the thumb, and its edges are formed by the tendons of three thumb-related muscles. On the radial (thumb-side) side, the tendons of abductor pollicis longus and extensor pollicis brevis run together, while on the ulnar side the tendon of extensor pollicis longus forms the other border. These three distal tendons together create the visible snuff box.

Why this fits the question: those three muscles—abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus—are the ones whose tendons outline the snuff box, whereas flexor pollicis longus and the thenar muscle abductor pollicis brevis lie in other areas and do not contribute to these borders.