Forearm

 ( Upper Limb Anatomy ) 

The forearm is the region of the upper limb between the Elbow-joint and the wrist.

The forearm contains two long , the radius and the ulna, forming the two radioulnar joints. The interosseous membrane connects these bones. Ultimately, the forearm is covered by skin, the anterior surface usually being less hairy than the posterior surface.

The forearm contains many muscles, including the flexors and extensors of the wrist, flexors and extensors of the digits, a flexor of the elbow (brachioradialis), and and that turn the hand to face down or upwards, respectively. In cross-section, the forearm can be divided into two fascial compartments. The posterior compartment contains the extensors of the hands, which are supplied by the radial nerve. The anterior compartment contains the flexors and is mainly supplied by the median nerve. The flexor muscles are more massive than the extensors because they work against gravity and act as anti-gravity muscles. The ulnar nerve also runs the length of the forearm.

The Radial artery and Ulnar artery and their branches supply the blood to the forearm. These usually run on the anterior face of the radius and ulna down the whole forearm. The main superficial veins of the forearm are the Cephalic vein, median antebrachial and the basilic vein. These veins can be used for cannularisation or venipuncture, although the cubital fossa is a preferred site for getting blood.

Distally, it articulates with the ulna again at the distal radioulnar joint. It forms part of the wrist joint by articulating with the Scaphoid bone at its lateral aspect and with the Lunate bone at its medial aspect.

Distally it forms part of the distal radioulnar joint and also articulates with the wrist.

! Compartment !! Level !! Muscle !! E/I !! Nerve

• "E/I" refers to "extrinsic" or "intrinsic". 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.
• The brachioradialis, flexor of the forearm, is unusual in that it is located in the posterior compartment, but it is actually in the anterior portion of the forearm.
• The anconeus is considered by some as a part of the posterior compartment of the arm.

See separate nerve articles for details on divisions proximal to the elbow and distal to the wrist; see Brachial plexus for the origins of the median, radial and ulnar nerves.

• Median nerve – interior nerve of the anterior compartment (pronator teres, FCR, Palmaris longus, FDS).
• anterior interosseous nerve (supplies FPL, lat. 1/2 of FDP, PQ).
• Radial nerve – supplies muscles of the posterior compartment (ECRL, ECRB).
• Superficial branch of radial nerve
• Deep branch of radial nerve, becomes Posterior interosseus nerve and supplies muscles of the posterior compartment (ED, EDM, ECU, APL, EPB, EPL, Extensor Indicis).
• Ulnar nerve – supplies some medial muscles (FCU, med. 1/2 of FDP).

• Brachial artery
• Radial artery
• Radial recurrent artery
• dorsal metacarpal artery
• Princeps pollicis artery
• Ulnar artery
• Anterior ulnar recurrent artery and posterior ulnar recurrent artery
• Common interosseous artery
• Posterior interosseous artery
• Anterior interosseous artery

• Interosseous membrane of forearm
• Annular ligament of ulna