Serratus Anterior Muscle Anatomy

Location & Overview

The serratus anterior is a fan-shaped muscle that is located on the thorax’s lateral wall. The serratus anterior muscle is located deep to the scapula, pectoralis major, and pectoralis minor. It is also deep to the subscapularis and it is separated from the subscapularis muscle by bursa or supraserratus bursa. It is possible to palpate the serratus anterior by pressing between the pectoralis major and latissimus dorsi muscles. In athletic individuals, with a low body fat percentage, it is often visible from the skin’s surface. It is usually divided into three different parts depending on the portion of its origin and insertion: serratus anterior inferior, serratus anterior intermediate, and serratus anterior superior. The specifics of the three sections are covered in further detail in the ‘origin and insertion’ section ^{[1] [2] [3]}.

The serratus anterior is also commonly referred to as the ‘boxer’s muscle’ due to its role in the mechanics of boxing and other striking sports. When a boxer throws a punch, this muscle aids in the extension and forward movement of the arm (protraction of the scapula), allowing for a more forceful and effective strike. Additionally, the serratus anterior contributes to maintaining scapular stability, which is vital for both offensive and defensive techniques in boxing ^{[4] [5]}.

Here we can see the serratus anterior muscle from an anterolateral view.

Here we can see the serratus anterior muscle from a lateral view.

Here we can see the serratus anterior muscle from a posterior view.

Here we can see the serratus anterior muscle seen from an anterior view.

Origin & Insertion

The serratus anterior is a muscle that wraps around the ribcage, originating from the first to either the eighth or ninth rib, before inserting onto the scapula. This muscle has three different parts, each connecting to different locations. The superior serratus anterior originates from the first and second ribs and inserts near the superior angle of the scapula. The intermediate serratus anterior originates from the third to sixth ribs and attaches along the medial border of the scapula. The inferior serratus anterior originates from the seventh to ninth ribs and inserts close to the scapula’s inferior angle. In some individuals, the serratus anterior may also originate from the tenth rib, or its origin may be absent from the first rib ^{[6] [7] [8]}.

Here we can see the serratus anterior’s origins marked out in red. The serratus anterior originates on the superolateral surfaces of the first to eighth or ninth ribs.

Here we can see the serratus anterior’s insertion marked out in blue. The serratus anterior inserts on the superior angle, medial border, and inferior angle of the scapula.

Actions

The primary function of the serratus anterior muscle is to move the scapula anterolaterally around the thorax (towards the front of the body), which is known as scapular protraction. In addition, the serratus anterior aids in the upward rotation of the scapula, working alongside the trapezius muscle. Upward scapular rotation is important for raising the arms up, due to tilting the glenoid cavity upward and by doing so maintaining joint alignment. The glenoid cavity is where the head of the humerus sits. When the shoulders remain in a fixed position, the serratus anterior can contribute to respiration by elevating the ribs. Each segment of the serratus anterior plays a distinct role: the superior segment serves as the main axis of rotation, the middle segment pulls the scapula forward, and the inferior segment facilitates upward scapular rotation ^{[9] [10]}. The serratus anterior’s superior segment provides a main axis of rotation; the middle segment pulls the scapula forward; the inferior segment can rotate the scapula upward ^{[11] [12] [13]}.

This image shows scapula protraction, a motion where the shoulder blade moves laterally and anteriorly along the rib cage (toward the front of the body). This movement occurs during actions such as reaching forward or pushing an object. The opposite of scapula protraction is scapula retraction. The serratus anterior’s primary action is scapula protraction.

This image shows scapula upward rotation, where the shoulder blade moves laterally and superiorly, tilting the glenoid cavity upward. This movement enables the arm to be raised overhead, while maintaining joint alignment. The opposite of scapula upward rotation is scapula downward rotation. Scapula upward rotation is another function of the serratus anterior.
The serratus anterior can also assist with respiration by lifting the ribs.

Innervation

Innervation of the serratus anterior is supplied by the long thoracic nerve (C5, C6, C7). The long thoracic nerve originates from the upper section of the superior trunk of the brachial plexus ^[14]. A way to remember the innervation is by remembering the mnemonic ‘SALT’ because the letters stand for ‘serratus anterior long thoracic’.

Pictured here we can see the long thoracic nerve which innervates the serratus anterior muscle with spinal roots from C5, C6, and C7.

Pictured here we can see the brachial plexus, which the long thoracic nerve is a part of.

Blood Supply

Blood is supplied to the serratus anterior via the lateral thoracic artery, superior thoracic artery, and the thoracodorsal artery ^[15].