Serratus Anterior Muscle Anatomy

Overview
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
Nerve Long thoracic nerve (C5, C6, C7)
Artery Lateral thoracic artery
Superior thoracic artery
Thoracodorsal artery

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].

serratus anterior muscle lateral view

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

serratus anterior muscle from an anterior view

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

serratus anterior muscle posterior view

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

Origin & Insertion

This serratus anterior wraps around the ribcage from its origin on the first to eighth or ninth ribs and then inserts onto the scapula. The three parts of the serratus anterior connect to different places. The serratus anterior superior originates on ribs 1 to 2 and inserts near the scapula’s superior angle. The serratus anterior intermediate originates on ribs 3 to 6 and inserts along the scapula’s medial border. The serratus anterior inferior originates on ribs 7 to 9 and inserts near the scapula’s inferior angle. In some individuals, the serratus anterior can originate from the tenth rib also, or its origin may be absent from the first rib. [4] [5] [6].

serratus anterior origin

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.

serratus anterio insertion

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 action of the serratus anterior is to pull the scapula anterolaterally around the thorax (protraction of the scapula). The serratus anterior is also able to assist in upward rotation of the scapula with help from the trapezius. Upward rotation of the scapula is a vital component of being able to elevate the arms. When the shoulders are in a fixed position, the serratus anterior can assist with respiration by elevating the ribs [7] [8]. 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 [9] [10] [11].

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 [12]. A way to remember the innervation is by remembering the word ‘SALT’ because the letters provide the acronym of ‘serratus anterior long thoracic’.

Blood Supply

Blood is supplied to the serratus anterior via the lateral thoracic artery, superior thoracic artery, and the thoracodorsal artery [13].

Want some flashcards to help you remember this information? Then click the link below:
Serratus Anterior Flashcards

References

References
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, 4, 7, 10 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, 6 Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincot Williams & Wilkins; 2017.
5, 8, 11 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.
9 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.
12 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.
13 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.