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 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.
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))
(Superior part: Anterior surface of superior angle
Middle part: Anterior surface of medial border
Inferior part: Anterior surface of inferior angle and medial border)
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)|
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.
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:
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).
The contraction of the entire serratus anterior leads to a 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 thoracic muscles with our quiz:
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).