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Serratus Anterior Muscle Anatomy

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Origin
  • Superolateral surfaces of the first to eighth or ninth ribs
Insertion
  • Superior angle, medial border, and inferior angle of the scapula
Action
  • Protraction of the scapula
  • Upward rotation of the scapula
  • Can assist with respiration by lifting the ribs
Innervation
  • Long thoracic nerve (C5, C6, C7)
Blood Supply
  • Lateral thoracic artery
  • Superior thoracic artery
  • Thoracodorsal artery
Last updated: Estimated Reading Time: 7 min

Location & Overview

The serratus anterior is a fan-shaped muscle located on the lateral wall of the thorax. The serratus anterior muscle is located deep to the scapula, pectoralis major, and pectoralis minor. It is also deep to the subscapularis and is separated from the subscapularis muscle by a bursa, the 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 at the skin’s surface. It is usually divided into three different parts depending on the portion of its origin and insertion: the serratus anterior inferior, serratus anterior intermediate, and serratus anterior superior. The specifics of the three sections are covered in further detail in the ‘Origin & 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.[3,4]

serratus anterior muscle seen from an anterolateral view
Here, we can see the serratus anterior muscle from an anterolateral view.
serratus anterior muscle from a lateral view
Here, we can see the serratus anterior muscle from a lateral view.
serratus anterior muscle posterior view
Here, we can see the serratus anterior muscle from a posterior view.
serratus anterior, anterior view
Here, we can see the serratus anterior muscle from an anterior view.

Origin & Insertion

The serratus anterior is a muscle that wraps around the rib cage, 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.[2,5,3]

serratus anterior origin
Here, we can see the serratus anterior’s origins marked in red. The serratus anterior originates on the superolateral surfaces of the first to eighth or ninth ribs.
serratus anterior insertion
Here, we can see the serratus anterior’s insertion marked in blue. The serratus anterior inserts on the superior angle, medial border, and inferior angle of the scapula.

Action & Function

The primary function of the serratus anterior muscle is to move the scapula anterolaterally around the thorax (toward 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, as it tilts the glenoid cavity upward and thereby maintains 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.[2,5,6]

Image of a person demonstrating the movement of scapula protraction.
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.
Image of a person demonstrating the movement of scapula upward rotation.
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. The long thoracic nerve arises from the C5, C6, and C7 nerve roots of the brachial plexus.[7] One way to remember the innervation is by using the mnemonic ‘SALT’, because the letters stand for ‘serratus anterior long thoracic’.

long thoracic nerve
Here, we can see the long thoracic nerve, which innervates the serratus anterior muscle with spinal roots from C5, C6, and C7.
brachial plexus
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 thoracodorsal artery.[8] These arteries arise from the axillary arterial system and help supply different regions of the lateral thoracic wall and serratus anterior muscle. The lateral thoracic artery contributes to the blood supply of the serratus anterior along the side of the chest, while the thoracodorsal artery, a branch of the subscapular artery, contributes to the lower and posterior portions of the muscle. The superior thoracic artery contributes to the upper thoracic region and may also contribute to the vascular supply of the superior part of the serratus anterior.[9]

References

  1. [1] Nasu H, Yamaguchi K, Nimura A, Akita K. An anatomic study of structure and innervation of the serratus anterior muscle. Surg Radiol Anat. 2012 Dec;34(10):921-8. doi: 10.1007/s00276-012-0984-1. Epub 2012 May 26. PMID: 22638721.
  2. [2] Lung K, St Lucia K, Lui F. Anatomy, Thorax, Serratus Anterior Muscles. (Updated 2021 Oct 7). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK531457/
  3. [3] Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2017.
  4. [4] Lung K, Lui F. Anatomy, Thorax, Long Thoracic Nerve. (Updated 2022 Jul 25). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535396/
  5. [5] Ekstrom RA, Bifulco KM, Lopau CJ, Andersen CF, Gough JR. Comparing the function of the upper and lower parts of the serratus anterior muscle using surface electromyography. J Orthop Sports Phys Ther. 2004 May;34(5):235-43. doi: 10.2519/jospt.2004.34.5.235. PMID: 15189015.
  6. [6] Gregg JR, Labosky D, Harty M, Lotke P, Ecker M, DiStefano V, Das M. Serratus anterior paralysis in the young athlete. J Bone Joint Surg Am. 1979 Sep;61(6A):825-32. PMID: 479228.
  7. [7] Laulan J, Lascar T, Saint-Cast Y, Chammas M, Le Nen D. Isolated paralysis of the serratus anterior muscle successfully treated by surgical release of the distal portion of the long thoracic nerve. Chir Main. 2011 Apr;30(2):90-6. doi: 10.1016/j.main.2011.02.003. Epub 2011 Mar 23. PMID: 21507700.
  8. [8] Gordon A, Alsayouri K. Anatomy, Shoulder and Upper Limb, Axilla. 2021 Jul 26. In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 31613503.
  9. [9] Arora Y, Nassereddin A, Agarwal S. Anatomy, Thorax, Superior Thoracic Arteries. In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553140/

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