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Palmar interossei muscles - want to learn more about it?

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Palmar interossei muscles

The palmar interossei are three muscles located in the metacarpus. They arise from the metacarpal bones of the index, ring and little finger and are innervated by the deep branch of the ulnar nerve. Together, those muscles work together to close your spread fingers.

Anatomy

Origin

The origin surfaces of these muscles are facing towards the middle finger:

  • Palmar interosseous muscle I: ulnar side of the index finger
  • Palmar interosseous muscle II: radial side of the ring finger
  • Palmar interosseous muscle III: radial side of the little finger

Palmar interossei muscles

Insertion

From there, the muscles insert at the dorsal aponeurosis and the base of the proximal phalanx of their respective finger. The middle finger itself does not have its own palmar interosseous.

Innervation

The nerve innervation is provided by the deep branch of the ulnar nerve (C8-Th1).

Recommended video: Palmar interossei muscles
Origins, insertions, innervation and function of the palmar interossei muscles.

Function

The most important function of the palmar interossei is the closing of spread fingers, which means the movement of the fingers towards the middle finger (adduction in the metacarpophalangeal joints [MCP]).

Adduction of the fingers

In detail, the first pulls the index finger medially whereas the second and third pull the ring and little fingers laterally. Functionally, the palmar interossei act antagonistically to the dorsal interossei in the MCP.

(mnemonic: DAB = Dorsals ABduct, PAD = Palmars ADduct).

However both muscle groups perform common functions, as they flex the fingers in the MCP and extend in the proximal and distal interphalangeal joints (PIP and DIP). An analogous muscle group can be found in the foot which fulfills identical movements in the toes (plantar interossei muscles).

An unexplored fourth muscle

Current literature assumes that there are three palmar interossei. Nevertheless, in 1858 the German anatomist Henle has described a fourth palmar interosseous between the thumb and the index finger (palmar interosseous of Henle).

At first, it was assumed that the fibers he found were not an independent muscle, but instead part of either the adductor pollicis or flexor pollicis brevis. However, newest studies have shown that most people actually do have one additional short hand muscle between the thumb and the index finger. At this point, it is not clarified how this unknown muscle should be classified and which function it fulfills.

Palmar interossei muscles - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 852,397 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2nd edition, Thieme Verlag (2007), p. 316-317
  • J. E. Muscolino: The muscular system manual – The skeletal muscles of the human body, 2nd edition, Elsevier Mosby (2005), p. 683-685
  • J. Witthaut/C. Leclercq: Der M. interosseus palmaris des Daumens, Handchirurgie Mikrochirurgie Plastische Chirurgie (1999), Thieme Verlag, Issue 21(1), p. 66-69
  • R. S. Susman/L. Nyati/ M. S. Jassal: Observations on the pollical palmar interosseous muscle (of Henle), The Anatomical Record (1999), Issue 254(2), p. 159-165

Author:

  • Achudhan Karunaharamoorthy

Illustrators:

  • Palmar interossei muscles - Yousun Koh
  • Adduction of the fingers - Paul Kim 
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Muscles of the hand

Phalanges of the hand

Main muscles of the upper extremity

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