Anatomy
Origin:
Posterolateral aspect of middle third of ulna and adjacent interosseous membrane.
Insertion:
Dorsal surface of base of the distal phalanx of thumb.
Key Relations:
-The tendon of extensor pollicis longus passes underneath the extensor retinaculum in its own compartment.
-Its tendon forms the posterior boundary of the anatomical snuffbox.
-One of the six muscles in the deep posterior compartment of the forearm.
Functions
-Extends the interphalangeal joint of the thumb
-Extends the carpometacarpal joint of the thumb
-Extends the metacarpophalangeal joint of the thumb
-Helps extend the hand at the wrist
e.g. as in releasing your grip on an object..
Supply
Nerve Supply:
Posterior interosseous nerve (C7,C8) (continuation of deep branch of the radial nerve).
Blood Supply:
Posterior interosseus artery.
Clinical
Is affected in radial nerve palsy.
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