Wikipedia

Forearm

This article is about the body part. For other uses, seeForearm (disambiguation).

Theforearmis the region of theupper limbbetween theelbowand thewrist.[1]The term forearm is used inanatomyto distinguish it from thearm,a word which is 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 ishomologousto the region of thelegthat lies between thekneeand theanklejoints, thecrus.

Forearm
The forearm is highlighted in magenta
Details
Identifiers
Latinantebrachium
MeSHD005542
TA98A01.1.00.024
TA2146
FMA9663
Anatomical terminology

The forearm contains two longbones,theradiusand theulna,[2]forming the two radioulnar joints. Theinterosseous membraneconnects 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 thewrist,flexors and extensors of the digits, a flexor of the elbow (brachioradialis), andpronatorsandsupinatorsthat turn the hand to face down or upwards, respectively. In cross-section, the forearm can be divided into twofascial compartments.The posterior compartment contains the extensors of the hands, which are supplied by theradial nerve.The anterior compartment contains the flexors and is mainly supplied by themedian nerve.The flexor muscles are more massive than the extensors because they work against gravity and act as anti-gravity muscles. Theulnar nervealso runs the length of the forearm.[3]

Theradialandulnar arteriesand 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 thecephalic,median antebrachialand thebasilic vein.These veins can be used for cannularisation orvenipuncture,although thecubital fossais a preferred site for getting blood.

Structure

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Bones and joints

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The bones of the forearm are theradius(located on the lateral side) and theulna(located on the medial side)

Bones of forearm, radius on left and ulna on the right

Radius

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Proximally, the head of the radius articulates with thecapitulum of the humerusand the radial notch of the ulna at theelbow.Thearticulationbetween the radius and the ulna at the elbow is known as theproximal radioulnar joint.

Distally, it articulates with the ulna again at thedistal radioulnar joint.It forms part of thewrist jointby articulating with thescaphoidat its lateral aspect and with thelunateat its medial aspect.

Ulna

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Proximally, thetrochlear notchof the ulna articulates with thetrochlea of the humerusand theradial notcharticulates with the head of the radius at theelbow.[4]

Distally it forms part of thedistal radioulnar jointand also articulates with thewrist.[5]

Muscles

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See also:Muscle table § Forearm
Compartment Level Muscle E/I Nerve
Anterior superficial flexor carpi radialis E median
Anterior superficial palmaris longus E median
Anterior superficial flexor carpi ulnaris E ulnar
Anterior superficial pronator teres I median
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
Anterior deep pronator quadratus I median
Posterior (see below) brachioradialis I radial
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
Posterior deep supinator I radial
Posterior deep anconeus I radial
  • "E/I" refers to "extrinsic" or "intrinsic". The intrinsic muscles of the forearm act on the forearm, meaning, across the elbow joint and theproximalanddistalradioulnar joints (resulting inpronationorsupination), whereas the extrinsic muscles act upon the hand and wrist. In most cases, the extrinsic anterior muscles areflexors,while the extrinsic posterior muscles areextensors.
  • The brachioradialis, flexor of the forearm, is unusual in that it is located in theposterior compartment,but it is actually in the anterior portion of the forearm.
  • Theanconeusis considered by some as a part of theposterior compartment of the arm.[6]

Nerves

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

Vessels

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Veins of the forearm and hand
Main article:Arterial tree of subclavian artery

Other structures

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Function

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The forearm can be brought closer to the upper arm (flexed) and brought away from the upper arm (extended) due to movement at theelbow.The forearm can also be rotated so that the palm of thehandrotates inwards (pronated) and rotated back so that the palm rotates outwards (supinated) due to movement at the elbow and thedistal radioulnar joint.[5]

Clinical significance

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Midshaft fracture of the radius and ulna

Afractureof 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 withtorus fracturesof the forearm splinting appears to work better than casting.[7] Genetically determined disorders likehereditary multiple exostosescan lead to hand and forearm deformities. Hereditary multiple exostoses is due growth disturbance of the epiphyses of the radius and ulna, the two bones of the forearm.[8]

Additional images

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  • 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.
  • Bones of the forearm - ulna (left) and radius (right)

See also

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References

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  1. ^WebMD (2009)."forearm".Webster's New World Medical Dictionary(3rd ed.). Houghton Mifflin Harcourt. p. 166.ISBN978-0-544-18897-6.
  2. ^"Forearm".The Lecturio Medical Concept Library.Retrieved2021-06-22.
  3. ^Mitchell, Brittney; Whited, Lacey (2020-08-15)."Anatomy, Shoulder and Upper Limb, Forearm Muscles".National Center for Biotechnology Information, U.S. National Library of Medicine.StatPearls Publishing LLC.Retrieved22 June2021.
  4. ^"Structure of The Forearm".The Lecturio Medical Concept Library.Retrieved2021-06-22.
  5. ^abStandring, Susan (2016).Gray's anatomy: the anatomical basis of clinical practice(Forty-first ed.). [Philadelphia].ISBN9780702052309.OCLC920806541.{{cite book}}:CS1 maint: location missing publisher (link)
  6. ^"Dissector Answers — Axilla & Arm".The University of Michigan. Archived fromthe originalon 3 January 2008.Retrieved2008-01-17.
  7. ^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.PMID26555307.S2CID25796224.
  8. ^El-Sobky TA, Samir S, Atiyya AN, Mahmoud S, Aly AS, Soliman R (2018)."Current paediatric orthopaedic practice in hereditary multiple osteochondromas of the forearm: a systematic review".SICOT-J.4:10.doi:10.1051/sicotj/2018002.PMC5863686.PMID29565244.
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