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There are generally twelve muscles in the posterior compartment of the forearm, which can be further divided into superficial, intermediate, and deep. Most of the muscles in the superficial and the intermediate layers share a common origin which is the outer part of the elbow, the lateral epicondyle of humerus.
The posterior interosseous nerve (or dorsal interosseous nerve/deep radial nerve) is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve.
It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm. Together the flexor pollicis longus, pronator quadratus, and flexor digitorum profundus form the deep layer of ventral forearm muscles. [2] The muscle is named from Latin 'deep bender of the fingers'.
The deep branch of the radial nerve (also known as posterior interosseous nerve by some authors) [5] [6]) pierces the supinator muscle, winds around the radius under the cover of supinator to reach posterior of forearm where it again pierces supinator and after which it is known as the posterior interosseous nerve. It pierces the posterior ...
The intrinsic muscles of the forearm act on the forearm, meaning, across the elbow joint and the proximal and distal radioulnar joints (resulting in pronation or supination), whereas the extrinsic muscles act upon the hand and wrist. In most cases, the extrinsic anterior muscles are flexors, while the extrinsic posterior muscles are extensors.
Despite the bulk of the muscle body being visible from the anterior aspect of the forearm, the brachioradialis is a posterior compartment muscle and consequently is innervated by the radial nerve. [5] Of the muscles that receive innervation from the radial nerve, it is one of only four that receive input directly from the radial nerve.
The supinator consists of two planes of fibers, between which passes the deep branch of the radial nerve.The two planes arise in common—the superficial one originating as tendons and the deeper by muscular fibers [2] —from the supinator crest of the ulna, the lateral epicondyle of the humerus, the radial collateral ligament, and the annular radial ligament.
The deep branch of the radial nerve winds to the back of the forearm around the lateral side of the radius between the two planes of fibers of the supinator, and is prolonged downward between the superficial and deep layers of muscles, to the middle of the forearm. The deep branch provides motor function to the muscles in the posterior ...