The video tutorial explains the extensor pollicis longus muscle, which is responsible for the thumbs up movement. It originates from the ulna and interosseous membrane, extending to the thumb's distal phalanx. The muscle extends the thumb at the metacarpophalangeal and interphalangeal joints, creating the thumbs up curve. The posterior interosseous nerve, a branch of the radial nerve, supplies motor innervation to this muscle.

Where does the extensor pollicis longus muscle originate?

• Lateral epicondyle of the humerus

• Medial surface of the tibia

• Anterior surface of the radius

• Posterior middle third of the ulna

What is the insertion point of the extensor pollicis longus muscle?

• Base of the first distal phalanx

• Base of the third metacarpal

• Base of the first proximal phalanx

• Base of the second metacarpal

Which joints does the extensor pollicis longus muscle extend?

• Interphalangeal and radiocarpal joints

• Radiocarpal and metacarpophalangeal joints

• Metacarpophalangeal and interphalangeal joints

• Carpometacarpal and interphalangeal joints

What is the primary function of the extensor pollicis longus muscle?

• Opposes the thumb

• Extends the thumb

• Abducts the thumb

• Flexes the thumb

Which nerve supplies the extensor pollicis longus muscle?

• Anterior interosseous nerve

• Median nerve

• Ulnar nerve

• Posterior interosseous nerve