German Contact Help Login Register

Serratus posterior muscles

Contents

Anatomy and supply

The serratus posterior muscles are two thin, superficial back muscles which lie above the intrinsic back musculature. Both originate from the spinous processes and attach on the ribs, which is why they are also referred to as spinocostal muscles.

  • Serratus posterior superior muscle: runs from the spinous processes of the C6 to T2 vertebrae caudolaterally to the 2nd to 5th ribs. This muscle is covered by the rhomboids and the trapezius.
  • Serratus posterior inferior muscle: originates from the thoracolumbar fascia as well as the spinous processes of the lower thoracic vertebrae and upper lumbar vertebrae. From there, it ascends craniolaterally to the 9th to 12th ribs. The latissimus dorsi lies above this muscle.

Both muscles are counted among the secondary back muscles, meaning that they migrated to the back in the course of embryogenesis. They are supplied by the intercostal nerves deriving from the anterior rami of the spinal nerves.

Serratus posterior superior muscle
Recommended video: Serratus posterior superior muscle
Origins, insertions, innervation and function of the serratus posterior superior muscle.

Function

The serratus posterior muscles contribute to the movement and stabilization of the vertebral column and the thorax. The serratus posterior superior elevates the ribs and thus supports the inspiration (accessory muscle of inspiration). Furthermore, the activation on both sides extends the thoracic vertebral column while a unilateral contraction rotates it to the opposite side. In contrast the serratus posterior inferior helps during expiration by depressing the ribs (accessory muscle of expiration). This muscle can also extend (bilateral contraction) and rotate (unilateral contraction) the spine.

Pathology

The disproportionate use of the serratus posterior superior and other back muscles (e.g. cradling the phone between ear and shoulder) can result in a condition known as the scapulocostal syndrome. It is characterized by pain and paresthesia along the medial border of scapula radiating to the neck, chest and upper extremities. Particularly pain felt in the little finger during palpation of the muscle is one of the classic signs. Clinically, the scapulocostal syndrome is easily mistaken for a lesion of the spinal nerves of the cervical vertebral column (cervical radiculopathy) which typically presents with numbness, muscle weakness and further neurological deficits (e.g. weak or absent reflexes). As differential diagnosis, arthritis or rotator cuff rupture should also be considered.

Get me the rest of this article for free
Create your account and you’ll be able to see the rest of this article, plus videos and a quiz to help you memorize the information, all for free. You’ll also get access to articles, videos, and quizzes about dozens of other anatomy systems.
Create your free account ➞
Show references

References:

  • D. Drenckhahn, J. Waschke: Taschenbuch Anatomie, Urban & Fischer Verlag/Elsevier (2008), p. 134-136
  • S. Waldmann: Atlas of uncommon pain syndromes, 3rd edition, Elsevier Saunders (2013), p. 60-61
  • R. Gautschi: Manuelle Triggerpunkt-Therapie, 2nd edition, Thieme Verlag (2013), p. 280-282

Author:

  • Achudhan Karunaharamoorthy

Illustrators:

  • Serratus posterior muscles - Yousun Koh 
© 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.

Continue your learning

Article (You are here)
Other articles
Well done!
Create your free account.
Start learning anatomy in less than 60 seconds.