Back of forearm – Superficial extensor muscles and Deep extensor muscles
These specimens show the superficial extensor muscles and the deep extensor muscles of the back of the forearm.
The back of the forearm consists of the extensor muscles. The extensor muscles bring about the extension of the wrist and the digits. Most of these muscles are supplied by the radial nerve and the posterior interosseous branch of the radial nerve. These muscles take origin from the lateral epicondyle (common extensor origin) of the humerus and insert into the lower end of forearm bones or into the digits. These tendons pass deep to the extensor retinaculum of the wrist.
Posterior interosseous nerve:
The posterior interosseous nerve is a branch of the radial nerve, given in the upper part of the forearm. It passes between the two heads of the supinator and enters the back of the forearm. It supplies the extensor muscles of the back of the forearm. Damage to the posterior interosseous nerve leads to a clinical condition known as the wrist drop. In this condition, the individual is unable to extend the wrist.
The Extensor retinaculum is situated along the wrist. This is formed by the thickened deep fascia of the forearm. It has six osseo-aponeurotic compartments though which the tendons of the extensor muscles pass. The extensor retinaculum prevents the bow-stringing of the tendons.