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Scalene Muscles - want to learn more about it?

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Scalene Muscles

The scalene muscles (Latin: “ladder”) are three paired cervical muscles running from the cervical vertebrae to the upper two ribs. Hereby they form a roof over the pleura and the upper thorax. The innervation is carried by direct branches of the cervical and brachial plexuses (C3-6).

The scalene muscles are subdivided into:

  • Anterior scalene muscle
  • Middle scalene muscle
  • Posterior scalene muscle
Key facts about scalene muscles
Anterior scalene muscle

Origin: anterior tubercle of transverse processes of vertebrae C3-C6

Insertion: anterior scalene tubercle of rib 1, superior border of rib 1 (anterior to subclavian groove)

Innervation: anterior rami of spinal nerves C4-C6

Function:

- bilateral contraction - neck flexion

- unilateral contraction - neck lateral flexion (ipsilateral), neck rotation (contralateral), elevates rib 1

Middle scalene muscle

Origin: posterior tubercles of transverse processes of vertebrae C3-C7

Insertion: superior border of rib 1 (posterior to subclavian groove)

Innervation: anterior rami of spinal nerves C3-C8

Function: neck lateral flexion, elevates rib 1

Posterior scalene muscle

Origin: posterior tubercles of transverse processes of vertebrae C5-C7

Insertion: external surface of rib 2

Innervation: anterior rami of spinal nerves C6-C8

Function: neck lateral flexion, Elevates rib 2

This article will discuss the anatomy and function of the scalene muscles.

Anatomy and supply

Recommended video: Scalene muscles
Origins, insertions, innervation and functions of the scalene muscles.

Scalenus anterior muscle

The anterior scalene muscle runs from the anterior tubercula of the transverse processes of the 3rd to 6th cervical vertebrae to the first rib.

Scalenus medius muscle

The middle scalene muscle originates at the posterior tubercula of the transverse processes of the 3rd to 7th cervical vertebrae and inserts at the first rib dorsally to the scalenus anterior muscle.

Scalenus posterior muscle

The posterior scalene muscle has its origin at the posterior tubercula of the transverse processes of the 5th to 7th cervical vertebrae and its insertion at the second rib.

Anterior, middle, and posterior scalene muscles (from left to right) - lateral view

The triangle between the scalenus anterior muscle, the scalenus medius muscle and the first rib form the interscalene triangle. The subclavian artery and the brachial plexus pass through this gap. In contrary, the subclavian vein runs ventrally from the scalenus anterior muscle.

Brachial plexus - lateral view

Function

Scalene muscles have three main functions:

  • The scalene muscles elevate the ribs, and therefore the thorax. For that reason, they are also considered as accessory muscles of inspiration.
  • Lateral flexion: a unilateral contraction bends the cervical spine to the side.
  • Ventral flexion: a bilateral contraction of the scalenus anterior muscle causes a bending of the cervical spine to the front.

Clinical Notes

A too narrow interscalene triangle compresses the brachial plexus and subclavian artery (Scalene syndrome) causing paresthesia, more rarely circulatory disturbances (e.g. edema, ischemia) and pain. Typically the ulnar side and the little finger are affected.

Causes of the Scalene syndrome may be, amongst others, a hypertrophy of the scalene muscles due to chronic overload and variations or deformities of the first rib.

Scalene 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 1,029,446 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:

  • D. Drenckhahn/J. Waschke: Taschenbuch Anatomie, 1.Auflage, Urban & Fischer Verlag/Elsevier (2008), S.189
  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2.Auflage, Thieme Verlag (2007), S.156-157
  • A. Waldeyer: Anatomie des Menschen, 17.Auflage, De Gruyter (2003), S.238
  • W. Hacke: Neurologie, 13.Auflage, Springer Verlag (2010), S.663-664
  • A. Hüter-Becker/M. Dölken: Physiotherapie in der Orthopädie, 1.Auflage, Thieme Verlag (2005), S.248-249

Author & Layout:

  • Achudhan Karunaharamoorthy
  • Christopher A. Becker

Illustrators:

  • Anterior, middle, and posterior scalene muscles (from left to right) - lateral view - Yousun Koh 
  • Brachial plexus - lateral view - Paul Kim
  • Lateral flexion of the neck - Paul Kim
  • Lateral flexion of the neck - 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.

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