MUSCLES-SUPERFICIAL EXTENSORS OF FOREARM

SUMMARY

FROM MEDIAL TO LATERAL:
1. EXTENSOR CARPI ULNARIS - arises from the common extensor origin. Inserts into 5th 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 5th 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 3rd MC base (note that ECRL inserts into 2nd MC base). Extends the wrist.

4. EXTENSOR CARPI RADIALIS LONGUS - arises from the lower 1/3 of the lateral supracondylar ridge. Inserts into the 2nd 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.