22nd November 2016
KEY POINTS:
The Serratus Anterior muscle can be divided into three divisions:
upper (rib 1 and 2 superior fascicles attached to the medial and superior borders of the scapula that form the superior angle)middle (rib 2 inferior and 3 fascicles that passed to the medial border)and lower (rib 4 to 8/9 fascicles attached at the inferior angle).
Suggested functional implications
Upper division:
Controls and anchors the superior angle during scapular rotation
Controls external rotation of the scapula by anchoring the superior angle.
Helps maintain relative upward rotation of the scapula - anchors the superior angle to ribs 1 and 2 (positioned inferior to the superior angle) and faciltiates optimum scapular orientation, by keeping the acromion above the superior angle
Middle division:
The rib 2 inferior (has the largest cross sectional area) - contributes to external rotation (controlling internal rotation) of the scapula at the acromioclavicular joint and produces protraction of the clavicle at the sternoclavicular joint.
Before protraction can occur, the line of action of the serratus anterior will pull the medial border and inferior angle of the scapula towards the chest wall, creating external rotation of the scapula.
Lower division:
Pulls the inferior angle laterally around the chest wall (away from the midline) with a primary role of upward rotation of the scapula and controlling downward rotation
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