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Anterior Compartment Muscles
First we’ll start with the anterior compartment muscles. These are of course, anterior assuming the arm is in the anatomical position .
In general, these are the flexors of the wrist and fingers and pronate the forearm. There is a superficial layer and a deep layer of muscles. Most of these originate from or near the medial epicondyle of the humerus. Remember the medial one is the larger condyle of the humerus. Most of the distal tendons are held in place at the wrist by the flexor retinaculum which forms the carpal tunnel.
Special mention to the following muscles:
Pronator teres: Pronator teres pronates the forearm, turning the hand posteriorly. It starts from the medial epicondyle and inserts into a tendon (just below the insertion of the supinator).
Pronator quadratus is a square shaped muscle and when it contracts, it pulls the lateral side of the radius towards the ulna, thus pronating the hand.
Flexor digitorum superficialis
Flexor digitorum profundus
Surface anatomy that is a must to know:
Tendon of Palmaris Longus: The palmaris longus tendon is what covers the entire palm of the hand.
Tendon of Flexor Carpi Radialis (immediately lateral to tendon of palmaris longus). Carpi refers to “wrist” (in Greek, carpi means to pluck).
Tendon of Flexor Digitorum Superficialis (immediately medial to tendon of palmaris longus) are the ones near your wrist.
Tendon of Flexor Carpi Ulnaris (medial to tendon of flexor digitorum superficialis)
Posterior Compartment Muscles of the forearm
Most of these originate from the lateral epicondyle. Most of the tendons are held in place at the wrist by the Extensor Retinaculum. These are extensors of the wrist and fingers and supinate the forearm. Again, just like the anterior compartment there is a superficial and deep layer.
Muscles of special note: Supinator
Surface anatomy to know:
Tendons of the Extensor Digitorum (on the back of the hand)
Anatomical Snuffbox (from medial to lateral) comprised of the tendons of the extensor pollicis brevis and extensor pollicis longus. In the picture, the longus is the tendon on top and the brevis on the bottom. Also, pollicis means thumb in latin. If you keep your hand flat on a table and move only your thumb up, it’s called retropulsion, and it’s created by the contraction of the extensor pollicis longus.
The supinator muscle helps uncross the radius from the ulna. The bicep can do the same because the bicep inserts into the radial tuberosity as well.
Here’s an excellent video that explains the movement of fingers: http://youtu.be/vlwAoKpSI7s
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The forearm is highlighted in magenta
| Anatomical terminology |
[ edit on Wikidata ]
The forearm is the region of the upper limb between the elbow and the wrist .  The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower “arm” is called the forearm. It is homologous to the region of the leg that lies between the knee and the ankle joints, the crus .
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 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 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.
- 1 Anatomy
- 1.1 Bones
- 1.2 Joints
- 1.3 Muscles
- 1.4 Nerves
- 1.5 Vessels
- 1.6 Other structures
- 2 Fracture
- 3 Additional images
- 4 See also
- 5 References
Anatomy[ edit ]
Bones[ edit ]
Joints[ edit ]
- Proximal to forearm
- In the forearm
- Proximal radioulnar joint
- Distal radioulnar joint
- Distal to forearm
Muscles[ edit ]
|Anterior||superficial||flexor carpi radialis||E||median|
|Anterior||superficial||flexor carpi ulnaris||E||ulnar|
|Anterior||superficial (or intermediate)||flexor digitorum superficialis (sublimis)||E||median|
|Anterior||deep||flexor digitorum profundus||E||ulnar + median|
|Anterior||deep||flexor pollicis longus||E||median|
|Posterior||superficial||extensor carpi radialis longus||E||radial|
|Posterior||superficial||extensor carpi radialis brevis||E||radial|
|Posterior||intermediate||extensor digitorum (communis)||E||radial|
|Posterior||intermediate||extensor digiti minimi (proprius)||E||radial|
|Posterior||superficial||extensor carpi ulnaris||E||radial|
|Posterior||deep||abductor pollicis longus||E||radial|
|Posterior||deep||extensor pollicis brevis||E||radial|
|Posterior||deep||extensor pollicis longus||E||radial|
|Posterior||deep||extensor indicis (proprius)||E||radial|
- “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 . 
Nerves[ edit ]
(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 ( 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[ edit ]
- 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
- Radial artery
Other structures[ edit ]
- Interosseous membrane of forearm
- Annular ligament of ulna
Fracture[ edit ]
Midshaft fracture of the radius and ulna
A fracture of the forearm can be classified as to whether it involves only the ulna ( ulnar fracture ), only the radius ( radius fracture ) or both ( radioulnar fracture )
For treatment of children with torus fractures of the forearm splinting appears to work better than casting, 
Additional images[ edit ]
Superficial muscles of the forearm
Deep muscles of the anterior forearm
Deep muscles of the posterior forearm
Cross-section through the middle of the forearm.
See also[ edit ]
- Forearm flexors
References[ edit ]
- ^ WebMD (2009). “forearm” . Webster’s New World Medical Dictionary (3rd ed.). Houghton Mifflin Harcourt. p. 166. ISBN 978-0-544-18897-6 .
- ^ “Dissector Answers — Axilla & Arm” . Archived from the original on 3 January 2008. Retrieved 2008-01-17.
- ^ Jiang, N; Cao, ZH; Ma, YF; Lin, Z; Yu, B (November 2016). “Management of Pediatric Forearm Torus Fractures: A Systematic Review and Meta-Analysis”. Pediatric Emergency Care. 32 (11): 773–778. doi : 10.1097/pec.0000000000000579 . PMID 26555307 .
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|Look up forearm in Wiktionary, the free dictionary.|
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