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Extensor Compartment of the : Deep layer

DEEP LAYER OF EXTENSORS

"true" deep layer Supinator o deep branch of radial nerve which pierces it on its way to transforming into the posterior interosseous nerve o originates from everywhere... the lateral humeral epicondyle, the radial collateral ligament, the annular ligament, the supinator fossa and the crest of ulna Attachments of the Supinator to the o inserts into the lateral posterior and anterior surfaces of Epicondyle of humerus the proximal third of radius Radial collateral ligament o it supinates the forearm, turning the to face anteriorly Annular ligament of radius Supinator and superiorly when the forearm is flexed. It is the Ulnar Supinator crest and fossa PRIME MOVER for slow unopposed suination Ulnar posterior surface o The supinator forms the floor of the cubital fossa together

with brachialis. It is a sheet-like muscle, and it envelops

the radius.

Interosseous membrane Extensor Indicis o Posterior interosseous nerve o originates from the posterior surface of the distal third of the ulna, and the interosseous membrane Abductor pollicis longus o inserts into the extensor expansion of the index finger

o extends the index finger, enabling independent extension o helps extend the at the wrist "outcropping" deep layer the Supinator wraps around the radius to insert into the anterior these originate from the proximal, middle and distal thirds of the ulna (as a surface of it. Together with the generalization). They emerge in the surface in the furrow that forms in the brachialis it forms the floor of extensor compartment the cubital fossa Abductor Pollicis Longus Extensor Pollicis Longus o Posterior interosseous nerve

o originates from the posterior surface of the proximal radius and ulna, as well as the interosseous membrane o inserts into the base of the 1st metacarpal, and occasionally also the trapezium. o abducts and extends the thumb at the carpometacarpal joint Extensor Pollicis Brevis o shares a common tendon sheath with the extensor pollicis brevis at the wrist

Extensor Indices Extensor Pollicis Brevis Which shares an extensor Common sheath for the o Posterior interosseous nerve tendon sheath with the tendons of the extensor o originates from the posterior surface of the distal third of Extensor Digitorum tendon pollicis brevis and abductor the ulna, and the interosseous membrane pollicis longus o inserts into the dorsum of the base of the proximal phalanx of the thumb o extends the proximal phalanx of the thumb at the metacarpophalangeal joint; also extends the carpometacarpal joints of the thumb. o partly covered by the abductor pollicis longus o its tendon is immediately medial to the APL o these two tendons form the anterior boundary of the . Extensor Pollicis Longus o Posterior interosseous nerve o originates from the posterior surface of the middle third of the ulna, and the interosseous membrane o inserts into the dorsum of the base of the distal phalanx Extensor digitorum tendon of the thumb o extends the distal phalanx of the thumb; also extends Extensor expansion the metacarpophalangeal and the carpometacarpal joints Medial band attaches to the base of of the thumb. It also rotates the thumb laterally. o It enjoys its own tendon sheath at the wrist; it passes the middle phalanx medially over the dorsal tubercle of radius, using it as a pulley. o the EPL forms the posterior border of the anatomical snuffbox

APL inserts into the base of 1st metacarpal Lateral bands attach to the EPB inserts into the base of proximal phalanx base of the distal phalanx EPL inserts into the base of distal phalanx The hood which attaches to the palmar tendon