Extensor compartments wrist5/31/2023 ![]() ![]() Posterior surface of the base of the 3rd metacarpalĮxtensor expansions of the index, middle, ring and little fingers Lateral epicondyle of the humerus via the common extensor tendon Posterior surface of the base of the 2nd metacarpal Lateral supracondylar ridge of the humerus Origin, Insertion, Action & Nerve Supply Muscle Note: Most sources I found classified the ECRB and ECU as fusiform, but at least one source contradicts that and classes them as bipennate muscles. Their fibers travel distally, down the back of the forearm, and insert on the back of the carpals, metacarpals and phalanges.Īll extensors are parallel-oriented fusiform muscles, except for the extensor digitorum, which has an oblique fiber orientation and a unipennate architecture. These muscles originate from different points on the posterior surfaces of the ulna and radius, and on the distal humerus. The EI, EPL, EPB and APL are part of the deep posterior compartment of the forearm, which also includes the supinator.The ECRL, ECRB, ED, EDM and ECU are classified as part of the superficial posterior compartment of the forearm, which also includes the brachioradialis.The individual wrist extensor muscles are as follows:Īll of these muscles belong to the posterior compartment of the forearm, a classification that can be subdivided into superficial and deep layers: The wrist extensors are a group of nine individual muscles on the back of the forearm that act on the wrist and fingers.Ĭollectively, their primary function is wrist extension, though they also help carry out other movements of the wrist and fingers.
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