Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: S: Serratus Anterior

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Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: S

Serratus Anterior

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed

This muscle may receive a slip from the tenth rib. Likewise, the highest digitation often has no attachment to the first rib, or the lower slips may be absent and the muscle may not be found below the seventh rib. In one study it was found that the number of digitations varied between seven and 12. The last digitation stopped at the seventh rib in 1%, eighth in 40%, ninth in 38%, tenth in 10%, and the eleventh rib in 0.5% of cases. The first digitation attached to the first rib in 75%, or to the fascia of the first rib in 21% of cases. In 3%, the attachment of the first digitation was the second rib.

The muscle sheet is composed of three parts, the middle of which may be defective, and the gap between upper and lower parts may be filled with connective tissue. Rarely, the muscle may be continuous with levator scapulae. Some slips passing from the first and second ribs to the vertebral border of the scapula and supplied by the dorsal scapular nerve may be looked upon as belonging to the rhomboid sheet and therefore as variations of those muscles. Other slips may extend to adjacent muscles. Slips arising from digitations on ribs 6 and 7 and joining pectoralis minor and coracobrachialis have been described as axillary arch muscles. See also listing for axillary arch.

The innervation of serratus anterior is from cervical nerves five through seven in the form of the long thoracic nerve. The axons from the fifth cervical nerve supply the first digitation and the sixth and seventh supply the remainder of the muscle mass. If axons are supplied by the eighth cervical nerve they supply the lowest digitations. All of the muscles that supply the upper limb are derivatives of the cervical myotomes, primarily the fifth through seventh but occasionally from the eighth. The developing muscle mass becomes attached to the ribs before joining the scapula. This fact is used to explain why the long thoracic nerve has a superficial, not deep, position on the muscle surface.

Syn.: m. serratus anticus, serratus magnus (Albinus), serratus anticus major (Henle), Grosser Sägemuskel, Le grand dentelé.

Unilateral Absence of Serratus Anterior.
Dissection specimen,
University of Iowa.

References

Henle, F. (1871) Handbuch der Muskelehre des Menschen, in Handbuch der systematischen Anatomie des Menschen. Verlag von Friedrich Vieweg und Sohn, Braunschweig.

Livini, F. (1905) Contribution a la morphologie du M. serratus anterior chez l'homme. Arch. Ital. Biol. 44:115-116.

Livini, F. (1907) Morphologia del M. serratus anterior nell'uomo. Arch. Ital. Anat. Embriol. 6:429-441.

Macalister, A. (1875) Observations on the muscular anomalies in the human anatomy. Third series with a catalog of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-130.

Schaefer, E.A., Symington, J. and T.H. Bryce., Eds. (1923) Quain's Elements of Anatomy, 11th ed. Longmans , Green and Co., London.

Takii, T., and M. Mori. (1952) A study on the tendineal arch of the upper part of the origin of the M. serratus anterior. Kumamoto Daigaku Igakubu Daiichi Kaibogakukyoshitsu Gyosekishu. 14:D1-D11. In Japanese.

Wood, J. (1868) Variations in human myology observed during the winter session of 1867-68 at King's College, London. Proc. Roy. Soc. Lond. B 17:483-525.

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