MUSCLES-SUPERFICIAL EXTENSORS OF FOREARM

SUMMARY

FROM MEDIAL TO LATERAL
1. Extensor carpi ulnaris: arises from the common extensor origin. Inserts into 5^th MC base. Extends & adducts the wrist.

2. Extensor digiti minimi: arises from the common extensor origin. Passing beneath the extensor retinaculum, the tendon usually splits into 2 and lies side by side on the 5^th MC. It becomes an expansion on the dorsum of the little finger. It assists the extensor digitorum in extending the wrist and little finger.

3. Extensor carpi radialis brevis: arises from the common extensor origin. Inserted into 3^rd MC base (note that ECRL inserts into 2^nd MC base). Extends the wrist.

4. Extensor carpi radialis longus: arises from the lower 1/3 of the lateral supracondylar ridge. Inserts into the 2^nd MC base. Extends & abducts the wrist.

5. Extensor digitorum: arises from the common extensor origin, its rounded belly in the middle of the forearm. Its 4 tendons pass under the extensor retinaculum to pass to the fingers where they form the dorsal expansions/extensor hoods. On the dorsum these tendons are interconnected by fibrous bands. Extends wrist ⟹ fingers.

6. All muscles are supplied by the posterior interosseous nerve (PIN), branch of the radial nerve.

Reference(s)

R.M.H McMinn (1998). Last’s anatomy: regional and applied. Edinburgh: Churchill Livingstone.
Gray, H., Carter, H.V. and Davidson, G. (2017). Gray’s anatomy. London: Arcturus.