Editing Forearm

{{short description|Region of the upper limb between the elbow and the wrist}}
{{About|the body part|other uses}}
{{Infobox anatomy
| Name        = Forearm
| Latin       = antebrachium
| Image       = Forearm labeled.png
| Caption     = The forearm is highlighted in magenta
| Width       = 150px
| Caption2    =
| Precursor   =
| System      =
| Artery      =
| Vein        =
| Nerve       =
| Lymph       =
}}
The '''forearm''' is the region of the [[upper limb]] between the [[Elbow-joint|elbow]] and the [[wrist]].<ref>{{cite book |author=WebMD |chapter=forearm |chapter-url=https://books.google.com/books?id=t8UfI3BH78wC&pg=PA166 |page=166 |year=2009 |title=Webster's New World Medical Dictionary |edition=3rd |publisher=Houghton Mifflin Harcourt |isbn=978-0-544-18897-6}}</ref> The term forearm is used in [[anatomy]] to distinguish it from the [[arm]], 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 is [[Homology (biology)|homologous]] to the region of the [[Human leg|leg]] that lies between the [[knee]] and the [[ankle]] joints, the [[Human leg#Structure|crus]].

The forearm contains two long [[bone]]s, the [[Radius (bone)|radius]] and the [[ulna]],<ref>{{cite web|url=https://www.lecturio.com/concepts/forearm/|title=Forearm|website=The Lecturio Medical Concept Library|access-date=2021-06-22}}</ref> forming the two radioulnar joints. The [[Interosseous membrane of forearm|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 [[pronator]]s and [[supinator]]s that turn the hand to face down or upwards, respectively. In cross-section, the forearm can be divided into two [[fascial compartment]]s. 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.<ref>{{cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK536975/ |title=Anatomy, Shoulder and Upper Limb, Forearm Muscles|last1=Mitchell  |first1=Brittney  |last2=Whited |first2=Lacey |publisher=StatPearls Publishing LLC. |date=2020-08-15 |website=National Center for Biotechnology Information, U.S. National Library of Medicine |access-date=22 June 2021}}</ref>

The [[Radial artery|radial]] and [[Ulnar artery|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 vein|cephalic]], [[Median antebrachial 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.

== Structure ==
===Bones and joints===
The bones of the forearm are the [[Radius (bone)|radius]] (located on the lateral side) and the [[ulna]] (located on the medial side)
[[File:Radius and Ulna - Forearm Bones.jpg|alt=Bones of forearm, radius on left and ulna on the right|thumb|Bones of forearm, radius on left and ulna on the right]]

==== Radius ====
Proximally, the head of the radius articulates with the [[capitulum of the humerus]] and the radial notch of the ulna at the [[elbow]]. The [[articulation (anatomy)|articulation]] between the radius and the ulna at the elbow is known as the [[Proximal radioulnar articulation|proximal radioulnar joint]].

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

==== Ulna ====
Proximally, the [[trochlear notch]] of the ulna articulates with the [[trochlea of the humerus]] and the [[radial notch]] articulates with the head of the radius at the [[elbow]].<ref>{{cite web |url=https://www.lecturio.com/concepts/forearm/|title=Structure of The Forearm|website=The Lecturio Medical Concept Library |access-date=2021-06-22}}</ref>

Distally it forms part of the [[Distal radioulnar articulation|distal radioulnar joint]] and also articulates with the [[wrist]].<ref name=":0">{{Cite book|title=Gray's anatomy : the anatomical basis of clinical practice|author=Standring, Susan|isbn=9780702052309|edition=Forty-first|location=[Philadelphia]|oclc=920806541|year = 2016}}</ref>

=== Muscles ===
{{See also|Muscle table#Forearm}}

{| class="sortable wikitable"
 ! 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|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|extensor digitorum (communis)]] || E || radial
 |-
 | Posterior || intermediate || [[extensor digiti minimi|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|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 the [[Proximal radioulnar articulation|proximal]] and [[Distal radioulnar articulation|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 of the arm|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]].<ref name="titleDissector Answers&nbsp;— Axilla & Arm">{{cite web|url=http://anatomy.med.umich.edu/musculoskeletal_system/axilla_ans.html |title=Dissector Answers&nbsp;— Axilla & Arm |access-date=2008-01-17 |archive-url=https://web.archive.org/web/20080103065905/http://anatomy.med.umich.edu/musculoskeletal_system/axilla_ans.html |archive-date=3 January 2008 |url-status=dead | publisher = The University of Michigan }}</ref>

===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]]&nbsp;– interior nerve of the anterior compartment ([[pronator teres|PT]], [[Flexor carpi radialis|FCR]], [[Palmaris longus|PL]], [[Flexor digitorum superficialis|FDS]]).
**[[anterior interosseous nerve]] (supplies [[flexor pollicis longus|FPL]], lat. 1/2 of [[Flexor digitorum profundus|FDP]], [[pronator quadratus|PQ]]).
*[[Radial nerve]]&nbsp;– supplies muscles of the posterior compartment ([[Extensor Carpi Radialis Longus|ECRL]], [[Extensor Carpi Radialis Brevis|ECRB]]).
**[[Superficial branch of radial nerve]]
**[[Deep branch of radial nerve]], becomes [[Posterior interosseus nerve]] and supplies muscles of the posterior compartment ([[Extensor Digitorum|ED]], [[Extensor Digiti Minimi|EDM]], [[Extensor Carpi Ulnaris|ECU]], [[Abductor Pollicis Longus|APL]], [[Extensor Pollicis Brevis|EPB]], [[Extensor Pollicis Longus|EPL]], [[Extensor Indicis|EI]]).
*[[Ulnar nerve]]&nbsp;– supplies some medial muscles ([[Flexor Carpi Ulnaris|FCU]], med. 1/2 of [[Flexor Digitorum Profundus|FDP]]).

===Vessels===
[[File:Veins of the forearm and hand.jpg|thumb|Veins of the forearm and hand]]
{{Main|Arterial tree of subclavian artery}}
*[[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]]

===Other structures===
*[[Interosseous membrane of forearm]]
*[[Annular ligament of radius|Annular ligament]] of ulna

== Function ==
The forearm can be brought closer to the upper arm ([[Flexion|flexed]]) and brought away from the upper arm ([[Anatomical terms of motion#Flexion and extension|extended]]) due to movement at the [[elbow]]. The forearm can also be rotated so that the palm of the [[hand]] rotates inwards ([[pronated]]) and rotated back so that the palm rotates outwards ([[supinated]]) due to movement at the elbow and the [[Distal radioulnar articulation|distal radioulnar joint]].<ref name=":0" />

== Clinical significance ==
[[File:FracRadUlnaMark.png|thumb|Midshaft fracture of the radius and ulna]]
A [[bone fracture|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 fracture]]s of the forearm splinting appears to work better than casting.<ref>{{cite journal | vauthors = Jiang N, Cao ZH, Ma YF, Lin Z, Yu B | title = Management of Pediatric Forearm Torus Fractures: A Systematic Review and Meta-Analysis | journal = Pediatric Emergency Care | volume = 32 | issue = 11 | pages = 773–778 | date = November 2016 | pmid = 26555307 | doi = 10.1097/pec.0000000000000579 | s2cid = 25796224 }}</ref>
Genetically determined disorders like [[hereditary multiple exostoses]] can 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.<ref>{{cite journal | vauthors = El-Sobky TA, Samir S, Atiyya AN, Mahmoud S, Aly AS, Soliman R | title = Current paediatric orthopaedic practice in hereditary multiple osteochondromas of the forearm: a systematic review | journal = SICOT-J | volume = 4 | pages = 10 | date = 2018 | pmid = 29565244 | pmc = 5863686 | doi = 10.1051/sicotj/2018002 }}</ref>

==Additional images==
{{gallery|height=150|width=150|file:Gray414.png|Superficial muscles of the forearm
 |file:Gray415.png|Deep muscles of the anterior forearm
 |file:Gray419.png|Deep muscles of the posterior forearm
 |file:Gray417_color.PNG|Cross-section through the middle of the forearm.
 |File:Arm_1_--_Smart-Servier.png|Bones of the forearm - ulna (left) and radius (right)
}}

== See also ==
*[[Forearm flexors]]

== References ==
{{Reflist}}
{{Commons category|Forearms}}
{{wiktionary|forearm}}

{{Human regional anatomy}}
{{Upper limb general}}
{{Authority control}}

[[Category:Forearm| ]]
[[Category:Upper limb anatomy]]