Serratus anterior muscle

Author: Achudhan Karunaharamoorthy, MD • Reviewer: Dimitrios Mytilinaios, MD, PhD
Last reviewed: November 29, 2023
Reading time: 9 minutes

Serratus anterior muscle (Musculus serratus anterior)

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 8th or 9th ribs and inserts at the anterior surface of the scapula. Due to its course it has a “serrated” or “saw-toothed” appearance.

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

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 (variably extends to rib 10 (+ external oblique muscle))
Insertion	Scapula (Superior part: Anterior surface of superior angle Middle part: Anterior surface of medial border Inferior part: Anterior surface of inferior angle and medial border)
Innervation	Long thoracic nerve (C5- C7) Mnemonics: 'SALT' (stands for serratus anterior - long thoracic) & 'C5, 6, 7 raise your arms to heaven!'
Blood supply	Superior and lateral thoracic arteries, thoracodorsal artery branches
Function	Scapulothoracic joint: Draws scapula anterolaterally, Suspends scapula on thoracic wall, Rotates scapula (draws inferiorly angle laterally)

Contents

Origin and insertion
Innervation
Blood supply
Function
Frequent questions
Clinical aspects
Sources

+ Show all

Origin and insertion

The serratus anterior muscle originates at the 1st to 8/9th rib and inserts at the anterior surface of the medial border of the scapula (extending from the superior to inferior angles). 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 8/9th rib → medial border and inferior angle of the scapula. (The lowest attachment may alternatively extend to the 10th rib in approximately 10% of the population, as well as blend with the external abdominal oblique muscle.)

The inferior part of the muscle is the most prominent and powerful one.

Wondering how you're going to revise the anatomy of the serratus anterior muscle? Our handy trunk wall muscle anatomy chart has your back.

Serratus anterior muscle seen in a human cadaver. Notice how the muscle fibers follow the course of the ribs onto which they attach.

Innervation

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

The innervation for the serratus anterior is very easy to remember if you just know the right mnemonics! 'SALT' stands for 'Serratus Anterior = Long Thoracic' and will help you remember the name of the nerve, while knowing 'C5, 6, 7 raise your arms to heaven!' means you'll never forget the nerve roots associated with it!

Learn everything about the muscles of the thoracic wall with our video tutorials, quizzes, labeled diagrams, and articles:

Blood supply

The vascular supply to the serratus anterior comes from the superior and lateral thoracic arteries (branches of the axillary artery) as well as branches from the thoracodorsal artery (branch of subscapular artery).

Function

The contraction of the entire serratus anterior leads to an anterolateral 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).

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.

Solidify your knowledge about the serratus anterior and other thoracic muscles with our quiz:

Frequent questions

What is the function of serratus anterior?

The contraction of the entire serratus anterior muscle moves the scapula forward and laterally along the ribs.

Isolated contraction of the inferior part of the muscle elevates the shoulder joint, enabling the arm to be raised beyond 90º.

Conversely, the superior part of the muscle depresses the scapula, acting antagonistically.

In addition, the serratus anterior aids in stabilizing the scapula within the shoulder. Finally, when the scapula is fixed, the muscle elevates the ribs and functions as an accessory inspiratory muscle.

Where is the serratus anterior located?

The serratus anterior is a fan-shaped muscle located at the lateral wall of the thorax. Its main parts lies deep to the scapula and the pectoral muscles. This muscle is easily palpated between the pectoralis major and latissimus dorsi muscles.

What innervates serratus anterior?

The serratus anterior muscle is innervated by the long thoracic nerve (C5-C7), a branch of the brachial plexus.

Where does serratus anterior attach?

The serratus anterior muscle originates at the 1st to 8/9th ribs and inserts at the anterior surface of the medial border of the scapula (extending from the superior to the inferior angles). It can be divided into three parts. The superior part attaches to the superior angle of the scapula, the intermediate part attaches to the medial border of the scapula and the inferior part attaches to the medial border and inferior angle of the scapula. The lowest attachment may even extend to the 10th rib in some individuals or blend with th eexternal abdominal oblique muscle.

The serratus anterior muscle originates and inserts on what structures?

The serratus anterior muscle originates at the 1st to 8/9th ribs, and inserts at the anterior surface of the medial border of the scapula (extending from the superior to inferior angles). The lowest attachment may even extend to the 10th rib in some individuals or blend with th eexternal abdominal oblique muscle.

How to palpate serratus anterior?

The easiest way to palpate the serratus anterior muscle is by having the patient either stand or lie supine with their arms flexed forward or pushing against resistance. This protracts the scapula, causing the serratus anterior to contract strongly. The examiner's fingers should be placed along the lateral aspect of the rib cage, just below the axilla. The serratus anterior is the serrated muscle attaching to the ribs.

What are the muscles that look like ribs?

In athletes, the serrated appearance of the serratus anterior muscle, which attaches to the 1st through 8th or 9th ribs, can often be observed. This appearance might give the impression that the ribs themselves are visible, when, in fact, it is the muscle's contour being seen.

Which muscle attaches to the anterior surface of the scapula and extends to the ribs?

The muscle that attaches to the anterior surface of the scapula and extends to the ribs is the serratus anterior muscle, which protracts the scapula (pulls it forward around the thorax), holds the scapula flat against the rib cage and assistis in upward rotation of the scapula (assisting in elevating the arm above 90º).

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).

Sources

All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines.

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
S. Standring (2016). Gray's Anatomy (41st ed.). Edinburgh: Elsevier Churchill Livingstone.

Illustrators:

Serratus anterior muscle (ventral view) - Yousun Koh
Long thoracic nerve (ventral view) - Yousun Koh
Trunk wall (cadaveric dissection) - Prof. Carlos Suárez-Quian

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