Forearm

The forearm is the structure on the upper limb, between the elbow and the wrist.^[1]. This term is used in anatomy to distinguish it from the arm (or upper arm).

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The human forearm

The forearm contains two long bones, the radius and the ulna, forming the radioulnar joint. 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 digits, a flexor of the elbow (brachioradialis), and pronators and supinators 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 ulnar nerve also runs the length of the forearm.

The radial and ulnar arteries, 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, 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.

Anatomy

Bones

• radius
• ulna

Joints

• proximal to forearm
  • elbow
• in the forearm
  • proximal radioulnar joint
  • distal radioulnar joint
• distal to forearm
  • wrist

Muscles

See also: Muscle table#ARM

• "E/I" refers to "extrinsic" or "intrinsic". In most cases, the extrinsic anterior muscles are flexors of the hand and wrist. The extrinsic muscles of the forearm 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.

Nerves

(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 - principle nerve of the anterior compartment (PT, FCR, PL, 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, EI).
• Ulnar nerve - supplies some medial muscles (FCU, med. 1/2 of FDP).

Vessels

Main article: Arterial tree of subclavian artery

• brachial artery
  • radial artery
    • radial recurrent artery
  • ulnar artery
    • pulminary archery
    • anterior ulnar recurrent artery and posterior ulnar recurrent artery
    • common interosseous artery
      • posterior interosseous artery
      • anterior interosseous artery

Other structures

• interosseous membrane of the forearm
• annular ligament of ulna

Additional images

References

1. ^ Forearm at eMedicine Dictionary