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Serratus anterior muscle - want to learn more about it?

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Serratus anterior muscle

The serratus anterior muscle is a fan-shaped muscle at the lateral wall of the thorax. Its main part lies deep under the scapula and the pectoral muscles. It is easy to palpate between the pectoralis major and latissimus dorsi muscles. In athletic bodies the muscle may be even visible to the naked eye along the ribs underneath the axilla.

The serratus anterior muscle originates from the 1st to 9th rib and inserts at the ventral surface of the scapula. Due to its course it has a “serrated” or “saw-toothed” appearance.

Key facts about the serratus anterior muscle
Origin Superior part: Ribs 1-2, Intercostal fascia
Middle part: Ribs-3-6
Inferior part: Ribs 7-8/9/10 (+ external oblique muscle)
Insertion

Superior part: Anterior and posterior surface of superior angle of scapula

Middle part: Anterior surface of entire medial border of scapula

Inferior part: Anterior and posterior surface of inferior angle of scapula

Innervation Long thoracic nerve (C5- C7)
Function Scapulothoracic joint: Draws scapula anterolaterally, Suspends scapula on thoracic wall, Rotates scapula (draws inferiorly angle laterally)

This article will discuss the anatomy of the serratus anterior muscle.

Anatomy

Origins and Insertions

The serratus anterior muscle originates at the 1st to 9th rib and inserts at the ventral surface of the medial border of the scapula. The muscle is further divided into three parts:

  • Superior part: 1st to 2nd rib → superior angle of the scapula
  • Intermediate part: 2nd to 3rd rib → medial border of the scapula
  • Inferior part: 4th to 9th rib → medial border and inferior angle of the scapula. This part is the most prominent and powerful one.

Innervation

The innervation is supplied by the long thoracic nerve (C5-7), a branch of the brachial plexus.

Long thoracic nerve - ventral view

Function

The contraction of the entire serratus anterior leads to a ventrolateral movement of the scapula along the ribs. Due to the pull of the inferior part at the lower scapula, the shoulder joint is shifted superiorly. This shifting now enables to lift the arm above 90° (elevation).

Recommended video: Serratus anterior muscle
Origins, insertions, innervation and functions of the serratus anterior muscle.

In contrast the superior part depresses the scapula and thus acts antagonistically. Another function of the serratus anterior is the active stabilization of the scapula within the shoulder. Finally in a fixed scapula the muscle lifts the ribs and acts as an accessory inspiratory muscle.

Clinical Aspects

A damage of the long thoracic nerve can lead to a functional loss of the serratus anterior. Common causes are operations in the axilla (e.g. lymph node removal), a compression due to carrying heavy loads (e.g. backpack) and trauma.

Typical symptoms include trouble elevating the arm and a generally unstable shoulder. Another classic sign is the medial “wing-like” tilting of the scapula (scapula alata).

Serratus anterior muscle - 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 1,009,054 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, 2.Auflage, Thieme Verlag (2007), S.294-295
  • J. E. Muscolino: The muscular system manual – The skeletal muscles of the human body, 2.Auflage, Elsevier Mosby (2005), S.214-217
  • P. Berlit: Klinische Neurologie, 3.Auflage, Springer Verlag (2011), S.345

Author:

  • Achudhan Karunaharamoorthy

Illustrators:

  • Serratus anterior muscle - ventral view - Yousun Koh
  • Long thoracic nerve - ventral view - 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.

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