- Movements of the wrist joint<\/li>
- Extension of the fingers<\/li>
- Supination<\/li><\/ul>\n\n\n\n
They can be divided into superficial<\/strong> and deep<\/strong> layers<\/strong>.<\/div><\/p>\n\n\n\n
\n\n\n\nAll of the muscles of the posterior compartment are innervated by the radial nerve<\/strong>.<\/p>\n\n\n\n
Superficial layer<\/h3>\n<\/span>\n\n\n
There are seven muscles are found in this layer, and they all originate from the supraepicondylar ridge<\/strong> and lateral epicondyle of the humerus<\/strong>, and, except for the brachioradialis and anconeus, arrive at the hand as tendons, forming the extrinsic extensors of the hand:<\/p>\n\n\n\n
- Brachioradialis<\/li>
- Extensor carpi radialis longus<\/li>
- Extensor carpi radialis brevis<\/li>
- Extensor digitorum muscle<\/li>
- Extensor digiti minimi<\/li>
- Extensor carpi ulnaris<\/li>
- Anconeus<\/li><\/ul>\n\n\n\n
![\"\"](\"https:\/\/meddists.com\/learn\/wp-content\/uploads\/2021\/02\/1120_Muscles_that_Move_the_Forearm_Antebrach._Sup._Ext._Sin1-1024x695.png\")
<\/a>Figure 1. Superficial muscles of the forearm (dorsal view)<\/strong><\/figcaption><\/figure>\n\n\n<\/span>\n Brachioradialis<\/h4>\n<\/span>\n\n\n
- The brachioradialis muscle<\/strong> crosses laterally the forearm from its humeral origin to insert on the lateral side of the distal end of the radius<\/strong>.<\/li>
- It has a strict relation with the radial nerve<\/strong>, which lies deep to it.<\/li>
- It flexes the elbow joint when the forearm is midpronated.<\/li><\/ul>\n\n\n<\/span>\n
Extensor carpi radialis longus<\/h4>\n<\/span>\n\n\n
- The extensor carpi radialis longus muscle lies deep to the brachioradialis muscle and inserts on the dorsal surface of the base of metacarpal II<\/strong>.<\/li>
- It extends and abducts the wrist joint.<\/li><\/ul>\n\n\n<\/span>\n
Extensor carpi radialis brevis<\/h4>\n<\/span>\n\n\n
- The extensor carpi radialis brevis lies deep to the extensor carpi radialis longus muscle and inserts on the dorsal surfaces of the bases of metacarpals II and III<\/strong>.<\/li>
- It extends and abducts the wrist joint.<\/li><\/ul>\n\n\n<\/span>\n
Extensor digitorum<\/h4>\n<\/span>\n\n\n
- The extensor digitorum muscle (sometimes known as the extensor digitorum communis<\/strong>) forms four tendons, one for each of the medial fingers, which are interconnected on the dorsal surface of the hand.<\/li>
- Each tendon inserts via the extensor hood<\/strong> to the base of the dorsal surfaces of the middle and distal phalanges<\/strong>.<\/li>
- It extends the four medial fingers.<\/li><\/ul>\n\n\n<\/span>\n
Extensor digiti minimi<\/h4>\n<\/span>\n\n\n
- The extensor digiti minimi muscle<\/strong> lies medial to the extensor digitorum muscle and inserts into the extensor hood of the little finger<\/strong>.<\/li>
- It extends the little finger.<\/li><\/ul>\n\n\n<\/span>\n
Extensor carpi ulnaris<\/h4>\n<\/span>\n\n\n
- The extensor carpi ulnaris muscle<\/strong> lies medial to the extensor digiti minimi and inserts into the medial side of the base of metacarpal V<\/strong>.<\/li>
- It extends and abducts the wrist joint.<\/li><\/ul>\n\n\n<\/span>\n
Anconeus<\/h4>\n<\/span>\n\n\n
- The triangular-shaped anconeus muscle<\/strong> lies most medially and inserts into the posterolateral surface of the olecranon and posterior surface of the ulna<\/strong>.<\/li>
- It abducts the ulna during pronation and extends the elbow joint.<\/li><\/ul>\n\n\n<\/span>\n
Deep layer<\/h3>\n<\/span>\n\n\n
Five muscles are found in this layer, and, except for the supinator muscle, all of them originate from the posterior surfaces of the radius, ulna, and interosseous membrane<\/strong>, and pass into the thumb and fingers:<\/p>\n\n\n\n
- Supinator<\/li>
- Abductor pollicis longus<\/li>
- Extensor pollicis brevis<\/li>
- Extensor pollicis longus<\/li>
- Extensor indicis<\/li><\/ul>\n\n\n\n
![\"\"](\"https:\/\/meddists.com\/learn\/wp-content\/uploads\/2021\/02\/1120_Muscles_that_Move_the_Forearm_Antebrach._Prof._Ext._Sin1-1024x625.png\")
Figure 2. Deep muscles of the forearm (dorsal view)<\/strong><\/figcaption><\/figure>\n\n\n<\/span>\n Supinator<\/h4>\n<\/span>\n\n\n
- The supinator muscle<\/strong> has two layers: the superficial originates from the lateral epicondyle of the humerus and the related anular and radial collateral ligaments of the elbow joint<\/strong>, and the deep layer originates from the ulna\u00b4s supinator crest<\/strong>.<\/li>
- Both layers insert into the lateral surface of the radius<\/strong>.<\/li>
- It supinates the forearm and hand.<\/li><\/ul>\n\n\n<\/span>\n
Abductor pollicis longus<\/h4>\n<\/span>\n\n\n
- The abductor pollicis longus muscle<\/strong> passes into the thumb and inserts on the lateral side of the base of metacarpal I<\/strong>.<\/li>
- It abducts the thumb.<\/li><\/ul>\n\n\n<\/span>\n
Extensor pollicis brevis<\/h4>\n<\/span>\n\n\n
- The extensor pollicis brevis muscle<\/strong> helps to form, along with the abductor pollicis longus muscle, the posterolateral bulge on the distal forearm.<\/li>
- It passes into the thumb and inserts on the dorsal surface of the base of the proximal phalanx<\/strong>.<\/li>
- It extends the thumb.<\/li><\/ul>\n\n\n<\/span>\n
Extensor pollicis longus<\/h4>\n<\/span>\n\n\n
- The extensor pollicis longus muscle<\/strong> passes into the thumb.<\/li>
- It inserts with its long tendon into the dorsal surface of the distal phalanx of the thumb<\/strong>.<\/li>
- It extends all joints of the thumb.<\/li><\/ul>\n\n\n<\/span>\n
Extensor indicis<\/h4>\n<\/span>\n\n\n
- The extensor indicis muscle<\/strong> passes into the hand from its ulnar origin.<\/li>
- It inserts into the extensor hood of the index finger<\/strong> along with the extensor digitorum muscle.<\/li>
- It extends the index finger.<\/li><\/ul>\n\n\n<\/span>\n
Additional resources<\/h3>\n<\/span>\n\n<\/span>\n
Dissection images<\/h4>\n<\/span>\n\n\n
![\"\"](\"https:\/\/meddists.com\/learn\/wp-content\/uploads\/2021\/01\/posterior-view-1024x576.png\")
<\/a>Figure 3. Posterior view<\/strong><\/figcaption><\/figure><\/li> ![\"\"](\"https:\/\/meddists.com\/learn\/wp-content\/uploads\/2021\/01\/lateral-1024x576.png\")
<\/a>Figure 4. Lateral view<\/strong><\/figcaption><\/figure><\/li> ![\"\"](\"https:\/\/meddists.com\/learn\/wp-content\/uploads\/2021\/01\/forearm_dissection9.png\")
<\/a>Figure 5. Posterior view<\/strong><\/figcaption><\/figure><\/li><\/ul><\/figure>\n\n\n<\/span>\n References and further reading<\/h4>\n<\/span>\n\n\n
- Fiac, Moore Keith MSc PhD Hon. DSc, et al.\u00a0Clinically Oriented Anatomy<\/em>. 8th ed., LWW, 2017. p721<\/strong><\/li>
- Faaa, Drake Richard PhD, et al.\u00a0Gray\u2019s Anatomy for Students<\/em>. 4th ed., Elsevier, 2019. p729<\/strong><\/li>
- Figures 1-2 by OpenStax, licensed under CC BY-SA 4.0<\/li>
- Figures 3-5 by Dr. Sanjoy Sanyal and Dr. Stancu George, licensed under CC BY-SA 4.0<\/li><\/ul>\n<\/span>
- Faaa, Drake Richard PhD, et al.\u00a0Gray\u2019s Anatomy for Students<\/em>. 4th ed., Elsevier, 2019. p729<\/strong><\/li>
- It inserts into the extensor hood of the index finger<\/strong> along with the extensor digitorum muscle.<\/li>
- It inserts with its long tendon into the dorsal surface of the distal phalanx of the thumb<\/strong>.<\/li>
- It passes into the thumb and inserts on the dorsal surface of the base of the proximal phalanx<\/strong>.<\/li>
- It abducts the thumb.<\/li><\/ul>\n\n\n<\/span>\n
- Both layers insert into the lateral surface of the radius<\/strong>.<\/li>
- The supinator muscle<\/strong> has two layers: the superficial originates from the lateral epicondyle of the humerus and the related anular and radial collateral ligaments of the elbow joint<\/strong>, and the deep layer originates from the ulna\u00b4s supinator crest<\/strong>.<\/li>
- It abducts the ulna during pronation and extends the elbow joint.<\/li><\/ul>\n\n\n<\/span>\n
- It extends and abducts the wrist joint.<\/li><\/ul>\n\n\n<\/span>\n
- It extends the little finger.<\/li><\/ul>\n\n\n<\/span>\n
- Each tendon inserts via the extensor hood<\/strong> to the base of the dorsal surfaces of the middle and distal phalanges<\/strong>.<\/li>
- It extends and abducts the wrist joint.<\/li><\/ul>\n\n\n<\/span>\n
- It extends and abducts the wrist joint.<\/li><\/ul>\n\n\n<\/span>\n
- It has a strict relation with the radial nerve<\/strong>, which lies deep to it.<\/li>
- The brachioradialis muscle<\/strong> crosses laterally the forearm from its humeral origin to insert on the lateral side of the distal end of the radius<\/strong>.<\/li>
![\"\"](\"https:\/\/meddists.com\/learn\/wp-content\/uploads\/2021\/02\/1120_Muscles_that_Move_the_Forearm_Antebrach._Sup._Ext._Sin1.png\")
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