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Abductor pollicis longus muscle

abductor pollicis longus muscle, abductor pollicis longus muscle actions
In human anatomy, the abductor pollicis longus APL is one of the extrinsic muscles of the hand As the name implies, its major function is to abduct the thumb at the wrist Its tendon forms the anterior border of the anatomical snuffbox

Contents

  • 1 Structure
    • 11 Innervation
    • 12 Blood supply
    • 13 Variation
  • 2 Function
  • 3 In other animals
  • 4 See also
  • 5 Explanations
  • 6 Notes
  • 7 Additional Images
  • 8 References

Structureedit

The abductor pollicis longus lies immediately below the supinator and is sometimes united with it It arises from the lateral part of the dorsal surface of the body of the ulna below the insertion of the anconeus, from the interosseous membrane, and from the middle third of the dorsal surface of the body of the radius1

Passing obliquely downward and lateralward, it ends in a tendon, which runs through a groove on the lateral side of the lower end of the radius, accompanied by the tendon of the extensor pollicis brevis1

The insertion is divided into a distal, superficial part and a proximal, deep part The superficial part is inserted with one or more tendons into the radial side of the base of the first metacarpal bone, and the deep part is variably inserted into the trapezium, the joint capsule and its ligaments, and into the belly of abductor pollicis brevis APB or opponens pollicis2

Innervationedit

The abductor pollicis longus muscle is innervated by the posterior interosseous nerve, which is a continuation of the deep branch of the radial nerve after it passes through the supinator muscle The posterior interosseous nerve is derived from spinal segments C7 & C83

Blood supplyedit

Abductor pollicis longus is supplied by the posterior interosseous artery4

Variationedit

An accessory abductor pollicis longus AAPL tendon is present in more than 80% of people and a separate muscle belly is present in 20% of people In one study, the accessory tendon was inserted into the trapezium 41%; proximally on the abductor pollicis brevis 22% and opponens pollicis brevis 5%; had a double insertion on the trapezium and thenar muscles 15%; or the base of the first metacarpal 1%5 Up to seven tendons have been reported in rare cases6

Multiple APL tendons can be regarded as a functional advantage since injured tendons can be compensated by the healthy ones7

Functionedit

The chief action of abductor pollicis longus is to abduct the thumb at the carpometacarpal joint, thereby moving the thumb anteriorly It also assists in extending and rotating the thumb4

By its continued action it helps to abduct the wrist radial deviation and flex the hand4

The APL insertion on the trapezium and the APB origin on the same bone is the only connection between the thumb's intrinsic and extrinsic musclesexplain 1 As the thumb is brought into action, these two muscles must coordinate to keep the trapezium stable in the carpus,2 which is important for the proper functioning of the thumb ie precision and power grip8

In other animalsedit

The only primates to have an APL completely separated from the extensor pollicis brevis are modern humans and gibbons9 In gibbons, however, the APL originates proximally on the radius and ulna, whereas it originates in the middle part of these bones in crab-eating monkeys, bonobos, and humans In all these primates, the muscle is inserted onto the base of the first metacarpal and sometimes onto the trapezium siamangs and bonobos and thumb sesamoids crab-eating monkeys10

In chimpanzees, the APL flexes the thumb rather than extends it like in modern humans Compared to the wrists of chimpanzees, the human wrist is derived compared to the Pan-Homo LCA in having considerably longer muscle moment arms for a range of hand muscles It is possible that these differences are due to supinated position of the trapezium in humans which, in its turn, is a result of the expansion of the trapezoid on the side of the palm11

A small, lens-shaped radial sesamoid embedded into the APL tendon is a primitive state found in all known Carnivora genera except in the red and giant pandas and the extinct Simocyon where it is hypertrophied enlarged into a sixth digit or a so called "false thumb", a derived trait that first appeared in ursids12 The APL sesamoid is present in all non-human primates, but only in about half of gorillas, and normally absent in humans13

See alsoedit

This article uses anatomical terminology; for an overview, see Anatomical terminology
  • Extensor pollicis longus
  • De Quervain syndrome
  • Bennett's fracture

Explanationsedit

  1. ^ The extrinsic thumb muscles are those originating in the forearm: extensor pollicis longus, extensor pollicis brevis, flexor pollicis longus, and abductor pollicis longus The intrinsic thumbs muscles originates in the hand: opponens pollicis, flexor pollicis brevis, adductor pollicis and abductor pollicis brevis

Notesedit

  1. ^ a b Gray's Anatomy 1918, see infobox
  2. ^ a b van Oudenaarde & Oostendorp 1995
  3. ^ "Abductor pollicis longus" GPnotebook Retrieved 25 September 2016 
  4. ^ a b c "Abductor pollicis longus" PT Central 1998 Retrieved 25 September 2016 
  5. ^ Bravo, Barco & Bullón 2010, Results For a dissection example see Fig 3 in Hazani et al 2008
  6. ^ Mehta et al 2009, Discussion
  7. ^ Mehta et al 2009, Conclusions
  8. ^ van Oudenaarde 1991, Introduction
  9. ^ Aversi-Ferreira et al 2011, Results and Discussion
  10. ^ Michilsens et al 2009
  11. ^ Tocheri et al 2008, The evolution of the hominin hand as evidenced by the fossil record
  12. ^ Salesa et al 2006
  13. ^ Le Minor 1994, Abstract

Additional Imagesedit

Referencesedit

Aversi-Ferreira, Tales Alexandre; Maior, Rafael Souto; Carneiro-e-Silva, Frederico O; Aversi-Ferreira, Roqueline A G M F; Tavares, Maria Clotilde; Nishijo, Hisao; Tomaz, Carlos 2011 "Comparative Anatomical Analyses of the Forearm Muscles of Cebus libidinosus Rylands et al 2000: Manipulatory Behavior and Tool Use" PLoS ONE 6 7/e22165 PMC 3137621  PMID 21789230 doi:101371/journalpone0022165  Bravo, Elena; Barco, Raul; Bullón, Adrian May 2010 "Anatomic Study of the Abductor Pollicis Longus: A Source for Grafting Material of the Hand" Clin Orthop Relat Res 468 5: 1305–1309 PMC 2853646  PMID 19760470 doi:101007/s11999-009-1059-4  Hazani, Ron; Engineer, Nitin J; Cooney, Damon; Wilhelmi, Bradon J 2008 "Anatomic Landmarks for the First Dorsal Compartment" Eplasty 8 e53: e53 PMC 2586286  PMID 19092992  Le Minor, JM 1994 "The sesamoid bone of musculus abductor pollicis longus os radiale externum or prepollex in primates" Acta Anat Basel 150 3: 227–31 PMID 7817720 doi:101159/000147623  Mehta, Vandana; Arora, Jyoti; Suri, Rajesh Kumar; Rath, Gayatri February 2009 "A Rare Quadruplicate Arrangement of Abductor Pollicis Longus Tendons — Anatomical and Clinical Relevance" Clinics 64 2: 153–155 PMC 2666473  PMID 19219322 doi:101590/S1807-59322009000200014  Michilsens, Fana; Vereecke, Evie E; D'Août, Kristiaan; Aerts, Peter September 2009 "Functional anatomy of the gibbon forelimb: adaptations to a brachiating lifestyle" J Anat 215 3: 335–354 PMC 2750765  PMID 19519640 doi:101111/j1469-7580200901109x  van Oudenaarde, E February 1991 "Structure and function of the abductor pollicis longus muscle" J Anat 174: 221–227 PMC 1256056  PMID 2032936  van Oudenaarde, E; Oostendorp, R A June 1995 "Functional relationship between the abductor pollicis longus and abductor pollicis brevis muscles: an EMG analysis" J Anat 186 Pt 3: 509–515 PMC 1167009  PMID 7559124  Salesa, Manuel J; Antón, Mauricio; Peigné, Stéphane; Morales, Jorge January 2006 "Evidence of a false thumb in a fossil carnivore clarifies the evolution of pandas" Proc Natl Acad Sci USA 103 2: 379–382 PMC 1326154  PMID 16387860 doi:101073/pnas0504899102  Tocheri, Matthew W; Orr, Caley M; Jacofsky, Marc C; Marzke, Mary W April 2008 "The evolutionary history of the hominin hand since the last common ancestor of Pan and Homo" J Anat 212 4: 544–562 PMC 2409097  PMID 18380869 doi:101111/j1469-7580200800865x 

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