Serratus anterior muscle

Last revised by Yoshi Yu on 5 Apr 2023

Serratus anterior muscle is one of the four muscles of the pectoral region.

  • origin: lateral surface of 1st to 8th or 9th ribs
  • insertion: medial border of the scapula
  • innervation: long thoracic nerve
  • action:
    • draws the scapula anteriorly against the chest wall
    • when the scapula is fixed, assists in respiration

The serratus anterior muscle arises from the lateral 1st to 8th or 9th ribs as muscle slips that run posterosuperiorly around the chest wall, under the scapula to insert onto the costal surface of the medial scapular border 2

Injury to the long thoracic nerve during axillary surgery causes winging of the scapula as serratus anterior no longer holds the scapula against the chest wall. 

Serratus anterior injuries can be seen in baseball pitchers and rowers, with varying degrees of severity including avulsion from the origin at the ribs 2.

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