Muscles of the Posterior Forearm




Muscles of the Posterior Forearm

 

The muscles discussed in this section include:

Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor carpi ulnaris
Extensor digitorum
Extensor digiti minimi
Extensor indicies
Extensor pollicis longus
Extensor pollicis brevis
Abductor pollicis longus
Anconeus

Muscles-in-the-Deep-Layer-of-the-Posterior-Forearm

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Helpful Hints:

extensor carpi radialis longus – (extend = increase angle; carpi = wrist; radi = radius; longus = long)
extensor carpi radialis brevis – (brevis = short)
extensor carpi ulnaris – (ulnar = ulna)
extensor digitorum – (digit = finger)
extensor digiti minimi – (mini = small)
extensor indicies – (indicis = index finger)
extensor pollicis longus – (pollex = thumb)
extensor pollicis brevis
abductor pollicis longus (abduct = to take away)
anconeus – (ankon = elbow)
*It will be seen that many ‘extensor’ muscles of the wrist share a very similar origin. They all originate near or on the lateral epicondyle of the humerus.

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The muscles of the forearm are a difficult area to study due to their smaller size and their close proximity to one another. However, after study of the intricacies of forearm muscle anatomy one gains a new respect for the muscles that allow us to have such dexterity in our hands.

Origin:

Extensor carpi radialis longus – This muscle originates from the distal 1/3 of the lateral supracondylar ridge of the distal humerus.
Extensor carpi radialis brevis – This muscle originates from the lateral epicondyle of the humerus.
Extensor carpi ulnaris – This muscle originates from the lateral epicondyle of the humerus, and the posterior shaft of the ulna.
Extensor digitorum – This muscle originates from the lateral epicondyle of the humerus.
Extensor digiti minimi – This muscle originates from the lateral epicondyle of the humerus.
Extensor indicies – This muscle originates from the posterior shaft of the ulna.
Extensor pollicis longus – This muscle originates from the posterior midshaft of the ulna
Extensor pollicis brevis – This muscle originates from the posterior midshaft of the radius.
Abductor pollicis longus – This muscle originates from the posterior midshaft of the ulna and radius, as well as the interosseous membrane.
Anconeus – This muscle originates from the lateral epicondyle of the humerus.

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Insertion:

Extensor carpi radialis longus – This muscle inserts onto the base of metacarpal 2.
Extensor carpi radialis brevis – This muscle inserts onto the base of metacarpal 3.
Extensor carpi ulnaris – This muscle inserts onto the base of metacarpal 5.
Extensor digitorum – This muscle inserts onto the posterior bases of the second and third phalanx of the four lesser fingers by way of four individual tendons.
Extensor digiti minimi – This muscle inserts onto the posterior base of the first phalanx of the fifth finger.
Extensor indicies – This muscle inserts onto the posterior base of the third phalanx of the index finger by joining with a portion of the extensor digitorum tendon.
Extensor pollicis longus – This muscle inserts onto the distal phalanx (phalanx #2) of the thumb (pollex).
Extensor pollicis brevis – This muscle inserts onto the proximal phalanx (phalanx #1) of the thumb.
Abductor pollicis longus – This muscle inserts onto the base of metacarpal 1.
Anconeus – This muscle inserts onto the olecranon process and proximal shaft of the ulna. (Note: Insertion point very close to point of origin.)

Action:

Extensor carpi radialis longus – The action of this muscle includes wrist joint extension and abduction.
Extensor carpi radialis brevis – The action of this muscle includes wrist extension and abduction.
Extensor carpi ulnaris – The action of this muscle includes wrist extension and adduction.
Extensor digitorum – The action of this muscle includes extension of the metacarpophalangeal joint and extension of the proximal and distal interphalangeal joints of the four lesser fingers; also wrist extension.
Extensor digiti minimi – The action of this muscle includes extension of the metacarpophalangeal joint of the fifth digit.
Extensor indicies – The action of this muscle includes extension of the proximal and distal interphalangeal joints of the index finger (digit 2).
Extensor pollicis longus – The action of this muscle includes extension of the metacarpophalangeal joint and interphalangeal joint of the thumb (pollex).
Extensor pollicis brevis – The action of this muscle includes extension of the metacarpophalangeal joint and interphalangeal joint of the thumb; also thumb and wrist abduction.
Abductor pollicis longus – The action of this muscle includes thumb and wrist abduction; also extension of the metacarpophalangeal joint and interphalangeal joint of the thumb.
Anconeus – The action of this muscle includes elbow joint extension.

Printable Charts:

large-anatomy-diagram-posterior-forearm-muscles

 

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printable-charts-anatomy-diagram-posterior-forearm-muscles




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